Accelerated Session Establishment In A Multimedia Gateway

ABSTRACT

A method of establishing a reduced setup time session through a gateway includes receiving a first capability message transmitted from the first terminal to the gateway and receiving a second capability message transmitted from the second terminal to the gateway. The method also includes processing the first capability message and the second capability message to form a third capability message and a fourth capability message. The method further includes transmitting a third capability message from the gateway to the first terminal and transmitting a fourth capability message from the gateway to the second terminal. Moreover, the method includes receiving a first request message transmitted from the second terminal to the gateway and transmitting a second request message from the gateway to the first terminal. Transmitting the second request message is performed independent of receiving the first request message. Additionally, the method includes receiving a first response message transmitted from the second terminal to the gateway and transmitting a second response message from the gateway to the first terminal. Transmitting the second response message is performed in response to receiving the first response message.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 60/735,270, filed Nov. 9, 2005, the specification of which isincorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field oftelecommunications. More particularly, the present invention relates toa method and apparatus for establishing sessions for Third Generation(3G) digital communications. Merely by way of example, the invention hasbeen applied to a performing accelerated session setup for terminalscommunicating through a gateway, but it would be recognized that theinvention may also include other applications.

Third Generation mobile networks allow their users access to a richcomplement of multimedia services including audio, video, and data. TheThird Generation Partnership Project (3GPP) is an industry consortiumformed to advance the technology and acceptance of 3G mobile networks.The 3GPP has defined the 3G-324M Technical Specification that defineshow terminals and the network interoperate in order to provide advancedservices. Additionally, the Third Generation Partnership Project 2(3GPP2) has adopted the 3G-324M Technical Specification.

The 3G-324M Technical Specification is based on the ITU-T (InternationalTelecommunication Union, Standardization Section) H.324 Recommendation,that is, 3G-324M can be seen as a specific configuration of the H.324Recommendation of the ITU-T. Other H.324-like terminals exist, such asH.324M terminals.

The 3GPP 3G-324M recommendations use and extend H.324 as follows:

1. The use of the ITU-T H.324 umbrella recommendation and its Annex C.This defines the overall videotelephony service, including H.223 andH.245.

2. The use of Annexes A and B of H.223 ITU-T.

3. The use of the mobile messaging facilities of H.245.

4. The use of specific audio and video codecs. For example, the GSM-AMRaudio codec and the H.263 video codec are recommended. Other audio andvideo codecs are proposed as options.

The 3GPP has defined a phased network evolution and has definedspecifications for “Release 99”, “Release 5,” and “Release 6” networksin a logical network migration. Most mobile networks today use circuitswitched interfaces and protocols (e.g., ISDN, ISUP, and TDM DSOs) inorder to connect to fixed network telephony subscribers.

In a 3G-324M environment, interaction between terminal endpoints and theintervening network can be classified into three areas: call signaling,session signaling, and media exchange.

Call signaling is used to set up the bearer channel between endpoints.In 3G-324M, the bearer channel is typically a 64 Kb/sec channel.

Session signaling is used to define the framing used on the bearerchannel, to negotiate media options, to create, identify, and controlthe operation of “logical channels” (which carry the media) within themultiplexed frames on the bearer, and to communicate control informationbetween endpoints (such as the carriage of user key-presses).

3 G operators and service providers may offer their videotelephonysubscribers equipped with 3G-324M terminals access to enhanced services(such as videoconferencing and videomail). They may also offer thesubscribers the option of reaching users on other networks (such as thepublic internet or corporate, private, or another company's packetnetworks) and to establish with them videotelephony and conferencingsessions. In order to offer such services, the operators and servicesproviders need to equip their networks with gateways that can provideprotocol translation between the 3G terminals (e.g., 3G-324M) and theprotocols of the services and/or users in the other networks. Forexample one protocol for multimedia communication that is used on thepacket networks (e.g., public internet or corporate packet networks) isthe ITU-T H.323 protocol. Another example protocol is the IETF (InternetEngineering Task Force) Session Initiation Protocol. Both H.323 and SIPare widely used as protocols for user or service connectivity in packetnetworks. There are variants on H.323 and SIP, that we call H.323-likeand SIP-like, respectively.

The translation of protocols between 3G-324M terminals and H.323 or SIPterminals or services is typically done by a gateway function. Thegateway converts the protocols including signaling, sessionestablishment, media, as well as transport between circuit and packets.

During the 3G-324M and H.323 session setup phase, Session Signaling isused by both endpoints to advertise their Terminal Capabilities, toarbitrate for Master or Slave (which determines other protocol behaviorslater), to add individual Multiplexer Table Entries and to open LogicalChannels. In a videotelephony application, two Logical Channels aretypically opened in each direction: one for audio data and one for videodata. Note that a Session Setup sequence in this case requires six oreight round trip messages.

Once a session is set up, Session Signaling is used by 3G-324M and H.323endpoints to communicate out of band control information, such as thetransport of DTMF digits (by the “User Input Indication” message).

In the case of SIP, the number of round trip messages to perform thesame functions is reduced, albeit at the loss of some flexibility.Although most SIP terminals use a different technique for transportingDTMF digits (they are sent inband in the media stream), SIP has thenotion of transporting out of band control information (by the INFOmethod).

Importantly, for Session Signaling protocols commonly used by multimediadevices today (e.g., 3G-324M, H.323, and SIP), there are two importantparts of the session setup for media: media negotiation and a mediaestablishment.

An implementation of GSS functionality is denoted a “Full Proxy GSS,” ifit faithfully and immediately relays requests and responses from oneterminal to the other.

A Full Proxy GSS is straightforward to implement, as there is often atrivial mapping between messages from one network to messages in theother. As an example, both 3G-324M/H.324 and H.323 specify the use ofthe H.245 protocol at the session signaling layer.

A Full Proxy GSS converts messages received by one call half into anequivalent message (of the destination terminal protocol) for the othercall half, with typically only some necessary modifications. As anexample, if a request is made by an endpoint to open or close a logicalchannel, this request is immediately sent to the other endpoint: ineffect, the Full Proxy GSS acts largely as an intelligent messagetranslator/forwarder, and its operations are driven by the actions ofthe endpoints.

FIG. 1 is a simplified diagram illustrating a conventional call setupprocedure between an H.324 device and an H.323 device using a proxygateway. As illustrated in FIG. 1, call setup through a proxying gatewayinvolves propagation of messages through the gateway from one terminalto the other with the minimal modifications needed for compatibility.The acknowledged messages incur a roundtrip delay on both sides of thegateway leading to a substantial slow down of the session setup for bothterminals as compared to the time it would take for a session to beestablished to a like terminal.

Further, the session setup including media is further delayed by thepropagation where the media is not transmitted from the H.323 deviceuntil after receipt of the OLCs Ack from the H.3245 device via theproxying gateway. Similarly media is not transmitted from the H.324device until after receipt of the OLCs Ack from the H.323 device via theproxying gateway. As a result, a caller experiences long delays betweenthe initial call setup messages and the delivery of media.

As mentioned with regard to the Full Proxy GSS and observed in FIG. 1,there are many similarities between the H.324 and H.323 protocols, inparticular their use of the H.245 control protocol. For this reason, thetwo protocols are sometimes referred to as H.32X protocols.

Interworking between 3G-324M and a SIP network is somewhat moreelaborate than interworking between 3G-324M and H.323, as SIP and RTSPuse SDP instead of H.245 to communicate media options. There are severaldifferent flavors of SDP, so for purposes of simplicity, we may refer tothem as SDP-like. However, the necessary mappings are readily available.

The apparent simplicity of the Full Proxy GSS comes with a cost. Inorder to accurately track the session state, the Full Proxy GSS must insome cases have detailed knowledge of the concrete protocols used by thecall halves, and must often duplicate state and logic that is present inthe concrete protocol implementations. In addition, since the Full ProxyGSS must track the session state of the underlying protocols, the statemachines in the Full Proxy GSS may often be as complicated as the statemachines of the underlying concrete protocols. Also, the Full Proxy GSSis substantially slower to set up a call than would be the case foreither of devices attached if they were directly connected to peers inthe same network, due to the propagation of messages andacknowledgements through both networks.

Thus, there is a need in the art for improved methods and systems foraccelerated call setup in telecommunications applications throughgateways.

SUMMARY OF THE INVENTION

According to the present invention, techniques related to the field oftelecommunications are provided. More particularly, the presentinvention relates to a method and apparatus for establishing sessionsfor Third Generation (3G) digital communications. Merely by way ofexample, the invention has been applied to a performing acceleratedsession setup for terminals communicating through a gateway, but itwould be recognized that the invention may also include otherapplications.

According to an embodiment of the present invention, a method ofestablishing a reduced setup time session through a gateway is provided.The session is conducted between a first terminal operating under afirst protocol and a second terminal operating under a second protocol.The method includes receiving a first capability message transmittedfrom the first terminal to the gateway and receiving a second capabilitymessage transmitted from the second terminal to the gateway. The methodalso includes processing the first capability message and the secondcapability message to form a third capability message associated withthe first capability message and a fourth capability message associatedwith the second capability message. The method further includestransmitting a third capability message from the gateway to the firstterminal, transmitting a fourth capability message from the gateway tothe second terminal, and receiving a first request message transmittedfrom the second terminal to the gateway. The first request message isrelated to a process for opening a second media channel adapted tosupport a transmission of a second media stream from the second terminalto the gateway. Additionally, the method includes transmitting a secondrequest message from the gateway to the first terminal. The secondrequest message is related to a process for opening a first mediachannel adapted to support a transmission of a first media stream fromthe gateway to the first terminal. Furthermore, transmitting the secondrequest message is performed independent of receiving the first requestmessage. Moreover, the method includes receiving a first responsemessage transmitted from the second terminal to the gateway. The firstresponse message is related to the process for opening the second mediachannel. The method also includes transmitting a second response messagefrom the gateway to the first terminal. Transmitting the second responsemessage is performed in response to receiving the first responsemessage.

According to another embodiment of the present invention, a method ofestablishing a reduced setup time session through a gateway is provided.The session is conducted between a first terminal operating under afirst protocol and a second terminal operating under a second protocol.The method includes receiving a first capability message transmittedfrom the first terminal to the gateway, receiving a second capabilitymessage transmitted from the second terminal to the gateway, processingthe first capability message and the second capability message to form athird capability message, and processing the first capability messageand the second capability message to form a fourth capability message.The method also includes transmitting the third capability message fromthe gateway to the first terminal and transmitting the fourth capabilitymessage from the gateway to the second terminal. The method furtherincludes receiving a first request message transmitted from the secondterminal to the gateway. The first request message is related to aprocess for opening a second media channel adapted to support atransmission of a second media stream from the second terminal to thegateway. Additionally, the method includes transmitting a second requestmessage from the gateway to the first terminal. The second requestmessage is related to a process for opening a first media channeladapted to support a transmission of a first media stream from thegateway to the first terminal and transmitting the second requestmessage is performed independent of receiving the first request message.Moreover, the method includes receiving a first response messagetransmitted from the second terminal to the gateway. The first responsemessage is related to the process for opening the second media channel.The method also includes transmitting a second response message from thegateway to the first terminal. Transmitting the second response messageis performed independent of receiving the first response message.

According to an alternative embodiment of the present invention, amethod of establishing a communication session through a gateway isprovided. The communication session is conducted between a firstterminal and a second terminal. The method includes performing a firstcapability negotiation process with the first terminal and performing asecond capability negotiation process with the second terminal. Thesecond capability negotiation process is performed independent of thefirst capability negotiation process. The method also includes receivinga media stream transmitted from the second terminal, processing themedia stream, providing a first temporal feature that enables a decoderto establish a decoder refresh point, and thereafter, transmitting thefirst temporal feature and the processed media stream to the firstterminal.

According to another alternative embodiment of the present invention, amethod of establishing a reduced setup time session between anH.32X-like terminal and a gateway is provided. The session operatesunder a predetermined protocol. The method includes receiving a secondcapability message transmitted from a second terminal to the gateway,receiving a first capability message transmitted from the H.32X-liketerminal to the gateway, and processing the first capability message toform a third capability message associated with the first capabilitymessage. The method also includes transmitting the third capabilitymessage from the gateway to the H.32X-like terminal after receiving thefirst capability message transmitted from the H.32X-like terminal andreceiving the second capability message transmitted from the secondterminal to the gateway. The method further includes transmitting arequest message from the gateway to the H.32X-like terminal. The requestmessage is related to a process for opening a media channel between thegateway and the H.32X-like terminal. Moreover, transmitting the requestmessage is performed independent of the capability negotiation processbetween the gateway and the second terminal. Additionally, the methodincludes receiving a response message transmitted from the H.32X-liketerminal to the gateway. The response message is related to the processfor opening the media channel. The method also includes receiving amedia stream transmitted from the H.32X-like terminal to the gatewayusing the media channel and transmitting the media stream from thegateway to the second terminal.

According to a specific embodiment of the present invention, a method ofestablishing a reduced setup time session between an H.324-like terminaland a gateway is provided. The session operates under a predeterminedprotocol. The method includes receiving a first capability messagetransmitted from the H.324-like terminal to the gateway, receiving asecond capability message transmitted from a second terminal to thegateway, and processing the first capability message and the secondcapability message to form a third capability message. The method alsoincludes transmitting the third capability message from the gateway tothe H.324-like terminal and transmitting a first enablement message fromthe gateway to the second terminal. The first enablement message isrelated to media transmission enablement for a first media stream fromthe second terminal to the gateway, The first enablement message istransmitted prior to receiving a second enablement message from thefirst terminal at the gateway. The second enablement message is relatedto media transmission enablement for a second media stream from thegateway to the first device. Moreover, the method includes receiving thefirst media stream at the gateway, processing the first media stream atthe gateway to provide a processed media stream, and transmitting theprocessed media stream as the second media stream from the gateway.

According to another specific embodiment of the present invention, amethod of establishing a reduced setup time session between a firstSIP-like terminal and a second SIP-like terminal is provided. Thesession is conducted between the first SIP-like terminal and the secondSIP-like terminal through a gateway. The method includes receiving afirst call setup message transmitted from the first SIP-like terminal tothe gateway. The first call setup message includes a first capabilitymessage. The method also includes transmitting a second call setupmessage from the gateway to the second SIP-like terminal, receiving asecond capability message transmitted from the second SIP-like terminalto the gateway, and transmitting a first capability response messagefrom the gateway to the first SIP-like terminal. The method furtherincludes transmitting a second capability response message from thegateway to the second SIP-like terminal, receiving a media streamtransmitted from the second SIP-like terminal to the gateway, processingthe media stream, and receiving an acknowledgment message transmittedfrom the first SIP-like terminal to the gateway. The acknowledgementmessage is received at the gateway after transmitting the secondcapability response message. Moreover, the method includes thereafter,transmitting the processed media stream from the gateway to the firstSIP-like terminal.

According to yet another specific embodiment of the present invention, amethod of establishing a reduced setup time session between a firstSIP-like terminal and a second SIP-like terminal is provided. Thesession is conducted through gateway. The method includes performing afirst session setup process between the first terminal and the gatewayand performing a second session setup process between the secondterminal and the gateway. The second session setup process is performedindependent of the first session setup process. The method also includesreceiving a media stream transmitted from the second SIP-like terminalto the gateway, processing the first media stream, and providing anintra-coded frame. The method further includes thereafter, transmittingthe intra-coded frame and the processed media stream from the gateway tothe first SIP-like terminal.

Numerous benefits are achieved using embodiments of the presentinvention in contrast with conventional techniques. For example, in anembodiment according to the present invention, benefits are provided inthe context of 3G Videotelephony services using 3G-324M and a MultimediaGateway (MMGW), as the decoupling of the Session Signaling on either legof the connection (3G-324M/MMGW and MMGW/SIP or MMGW/H.323 or MMGW/RTSP)permits either side of the MMGW to proceed with its session setup asfast as possible. The 3G-324M Session Signaling may involve a number ofsequential protocol message exchanges, and the decoupling permits theprotocol procedures to proceed at their highest speed without beingheld-up unnecessarily by exchanges or messages on the other-side, andvise-versa. This is in contrast with a “proxy” approach where protocolmessages transmitted by one end-point are received and translated to theequivalent target protocol and transmitted by the MMGW to the otherterminal (which could be a handset or a server).

In embodiments utilizing a Decoupled GSS Architecture, session setupdelays are reduced or minimized and isolation is provided betweenimplementations of the concrete protocols. This reduces the overallcomplexity of the implementation and creates a framework wherebyadditional network features and interfaces can be added easily.

Depending upon the embodiment, one or more of these benefits may exist.These and other benefits have been described throughout the presentspecification and more particularly below. Various additional objects,features and advantages of the present invention can be more fullyappreciated with reference to the detailed description and accompanyingdrawings that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram illustrating a conventional call setupprocedure between an H.324 device and an H.323 device using a proxygateway;

FIG. 2 is a simplified diagram illustrating a call setup procedurebetween an H.324-like device and an H.323-like device using a fullydecoupled gateway according to an embodiment of the present invention;

FIG. 3 is a simplified diagram illustrating a call setup procedurebetween an H.324-like device and an H.323-like device using a capabilitycoupled gateway according to an embodiment of the present invention;

FIG. 4 is a simplified diagram illustrating a call setup procedurebetween an H.324-like device and a SIP-like device using a capabilitycoupled gateway according to an embodiment of the present invention;

FIG. 5 is a simplified diagram illustrating an alternative call setupprocedure between an H.324-like device and a SIP-like device using acapability coupled gateway according to an embodiment of the presentinvention;

FIG. 6 is a simplified diagram illustrating a call setup procedurebetween an H.324-like device and an RTSP-like device using a capabilitycoupled gateway according to an embodiment of the present invention;

FIG. 7 is a simplified diagram illustrating a call setup procedurebetween an H.324-like device and an H.323-like device using a capabilitycoupled gateway with a dynamic generation feature according to anembodiment of the present invention;

FIG. 8 is a simplified diagram illustrating a call setup procedurebetween an H.324-like device and an SIP-like device using a capabilitycoupled gateway with a dynamic generation feature according to anembodiment of the present invention;

FIG. 9 is a simplified diagram illustrating a call setup procedurebetween an H.324-like device and an RTSP-like device using a capabilitycoupled gateway with a dynamic generation feature according to anembodiment of the present invention;

FIG. 10 is a simplified diagram illustrating a call setup procedurebetween a first device implementing an accelerated procedure and anH.324-like device implementing an accelerated procedure using a gatewayaccording to an embodiment of the present invention;

FIG. 11 is a simplified call flow illustrating call establishment froman H.323 device implementing an accelerated procedure through a gatewayto an H.324 device implementing an accelerated procedure according to anembodiment of the present invention;

FIG. 12 is a simplified diagram illustrating a call setup procedurebetween an H.324-like device implementing an accelerated procedure and adevice implementing an accelerated procedure using a gateway accordingto an embodiment of the present invention;

FIG. 13 is a simplified call flow illustrating call establishment froman H.324 device implementing an accelerated procedure through a gatewayto an H.323 device implementing an accelerated procedure according to anembodiment of the present invention;

FIG. 14 is a simplified diagram of messaging flow between components ina gateway illustrating media activation in a media gateway supporting adynamic generation feature according to an embodiment of the presentinvention;

FIG. 15 illustrates components of a Decoupled Gateway Session SignalingArchitecture according to an embodiment of the present invention;

FIG. 16 illustrates message flows between various components of agateway during call establishment in some embodiments of the presentinvention;

FIG. 17 is a simplified diagram of messaging flow between components ina gateway illustrating media activation in a media gateway according toan embodiment of the present invention;

FIG. 18 illustrates how a state machine can control the establishment ofa session in a gateway with synchronization points according to anembodiment of the present invention;

FIG. 19 is a messaging flow between components in a gateway illustratingsession setup between an H.324-like terminal and a SIP-like terminal ina media gateway according to an embodiment of the present invention;

FIG. 20 is a simplified diagram illustrating a call setup procedurebetween an H.324-like device and a SIP-like device using a capabilitycoupled gateway with a dynamic generation feature according to anembodiment of the present invention;

FIG. 21 is a simplified diagram illustrating a call setup procedurebetween a first SIP-like device and a second SIP-like device using acapability coupled gateway according to an embodiment of the presentinvention; and

FIG. 22 is a simplified diagram illustrating a call setup procedurebetween a first SIP-like device and a second SIP-like device using acapability coupled gateway with a dynamic generation feature accordingto an embodiment of the present invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

According to an embodiment of the present invention, a method andapparatus for providing decoupled gateway session signaling is provided.More particularly, the present invention relates to a method andapparatus for establishing sessions for Third Generation (3G) digitalcommunications. Merely by way of example, the invention has been appliedto a performing accelerated session setup for terminals communicatingthrough a gateway, but it would be recognized that

Embodiments of the present invention relate to the signaling and sessionestablishment parts of the gateway function. Note that although wemention a gateway function, the function may be implemented in astand-alone system or can be part of another system. We will call such afunction the Multimedia Gateway (MMGW).

Call Signaling functions are an optional function of the MMGW. CallSignaling might also be performed as a function of a MMGW, typicallycalled Media Gateway Controller (MGC) function. The MGC function may beimplemented as a stand-alone system or may be part of another system. Aninterface typically exists between the MGC and the MMGW to communicateresults of the call signaling phase of the call. The typical protocolsused at this interface are MGCP and H.248/Megaco. As embodiments of thepresent invention relate to the session signaling function in the MMGW,it is immaterial whether the call signaling function is integral to theMMGW, and so it is assumed with no loss of generality that this is thecase.

The MMGW connects at the network boundary for two separate networks, andterminates the call and session signaling for the two networks. When aninter-network call is established, the MMGW terminates both call andsession signaling from the originating endpoint. To progress the call toits final destination endpoint, the MMGW originates both call andsession signaling in the destination network. It is convenient to referto the two legs of the connection (originating endpoint to MMGW, andMMGW to destination endpoint) as “half calls.”

An important example of 3G-324M interworking is between a videotelephonyuser (using a video enabled mobile handset) on a mobile network and avideotelephony user in the packet (e.g., Internet) network, using H.323or SIP.

The interfaces at the 3G-324M network boundary are usually ISDN or ISUPfor call signaling, H.245/3G-324M for session signaling, H.223 for themultiplexer layer on the bearer channel, and within the multiplexedframes the media and/or data bitstream chunks.

The interfaces at the network boundary of an H.323 packet network areusually H.225.0 and Q.931 for call signaling, H.245/H.323 for sessionsignaling. RTP is used for media payload encapsulation, packet tracking,and synchronization.

The interface at the network boundary of a SIP based packet network useSIP for call signaling. The media negotiation is typically performedusing an SDP-like protocol, and the media and data are transmitted usingRTP or a variation of RTP (RTP-like).

There are other networks of interest. For example, ISDN networks asspecified in ITU-T Recommendation H.320 have been in use for many years.Also less media rich networks such as the Public Switched TelephoneNetwork (PSTN) and voice only GSM or CDMA (IS-95) networks are capableof service enhancement when connecting through a gateway. It is furtherexpected that additional networks may appear over time, such as the NextGeneration Networks (NGN) such as ITU-T H.325. As before,internetworking is required to allow users of these diverse networksaccess to users in other networks, and similar comments andconsiderations apply.

There are also other services of interest, for example the provision ofcontent streaming services to 3G-324M subscriber. In this context, the3G user dials a content provision service such as movie clips or maturecontent. The access of the service on the 3G side would be through the3G-324M bearer. The Multimedia Gateway would terminate the call and actsas a mediator with a content access server through a protocol such asthe Real Time Streaming Protocol (RTSP and RTSP2) which is a protocolwith similarities to SIP on the packet side.

FIG. 2 is a simplified diagram illustrating a call setup procedurebetween an H.324-like device and an H.323-like device using a fullydecoupled gateway according to an embodiment of the present invention.As illustrated in FIG. 2, the setup operations for the H.324 and H.323devices are decoupled, each side of the gateway negotiates its sessionindependently from the other side. This system delivers quick sessionsetup by utilizing several procedures to ensure media compatibility aswell as various other capabilities, such as adaptation layer, and bitrate as well as media free of corruption.

In an embodiment of the present invention, a method of establishing acommunication session through a gateway is provided. The communicationsession is conducted between a first terminal and a second terminal.Merely by way of example, the first terminal may be an H.324-liketerminal (e.g., a 3G-324M handset) and the second terminal may be anH.323-like terminal.

The method includes performing a first capability negotiation processwith the first terminal and performing a second capability negotiationprocess with the second terminal. The second capability negotiationprocess is performed independent of the first capability negotiationprocess. As an example, the first capability negotiation process mayinclude the transmission of a first terminal capability set message fromthe gateway to the first terminal and the second capability negotiationprocess may include the transmission of a second terminal capability setmessage from the gateway to the second terminal.

The method also includes receiving a media stream transmitted from thesecond terminal, processing the media stream, providing a first temporalfeature that enables a decoder to establish a decoder refresh point, andthereafter, transmitting the temporal feature and the processed mediastream to the first terminal.

According to an embodiment, processing the media stream includesidentifying a second temporal feature in the media stream that enables adecoder to establish a decoder refresh point. The second temporalfeature may be an intra-coded frame. In another embodiment, processingthe media steam further includes generating a VideoFastUpdate, or asimilar VideoFastUpdate-like message, and transmitting theVideoFastUpdate or VideoFastUpdate-like message from the gateway to thesecond terminal. In yet another embodiment, the first temporal featureis an intra-coded frame, generated, for example, by converting aninter-coded frame into an intra-coded frame at the gateway.Alternatively, the first temporal feature may be an intra-coded frameprovide by a video transcoder.

In a particular embodiment, processing the media stream includesidentifying a second temporal feature in the media stream that enables adecoder to establish a decoder refresh point. For example, the secondtemporal feature may be an intra-coded frame.

In a specific embodiment, the first capability negotiation processincludes the transmission of a first terminal capability set messagefrom the gateway to the first terminal and the second capabilitynegotiation process includes the transmission of a second terminalcapability set message from the gateway to the second terminal. Thefirst terminal may be an H.324-like terminal (e.g., a 3G-324M handset)and the second terminal may be an H.323-like terminal.

It should be appreciated that the specific steps illustrated in FIG. 2provide a particular method of establishing a communication sessionthrough a gateway according to an embodiment of the present invention.Other sequences of steps may also be performed according to alternativeembodiments. For example, alternative embodiments of the presentinvention may perform the steps outlined above in a different order.Moreover, the individual steps illustrated in FIG. 2 may includemultiple sub-steps that may be performed in various sequences asappropriate to the individual step. Furthermore, additional steps may beadded or removed depending on the particular applications. One ofordinary skill in the art would recognize many variations,modifications, and alternatives.

Media, or codec, compatibility can be achieved on each side in a numberof ways. A simple way that will limit the ability of handsets to utilizetheir best quality media codecs is to restrain to a single mandatorycodec, or single supported codec, for outgoing capabilities from thegateway, regardless of the terminals abilities, including any additionalcommon non-mandatory codec abilities. This will provide a mode ofoperation in which only a single codec can be selected, for exampleH.263 video on both sides allowing media pass through. If incompatiblecodecs are mandated on the two sides, the introduction of a singletranscoder will allow this method to continue to work. For example,G.723.1 on H.323 and GSM-AMR on the H.324 (3G-324M) side could be joinedby introducing a transcoder between GSM-AMR and G.723.1. In anembodiment, a pair of unidirectional transcoders are utilized. Such atranscoder is shown in commonly assigned U.S. Pat. No. 6,829,579, issuedon Dec. 7, 2004, which is incorporated by reference in its entirety forall purposes. Alternatively, the transcoder may be a simple tandemtranscoder made up of a decoder and an encoder.

Media, or codec, compatibility can further be ensured by introducingmultiple transcoders between many codec types. By way of example,further transcoders are described more fully in commonly assigned andco-pending U.S. patent application Ser. No. 10/620,329, filed on Jul.14, 2003, which is incorporated by reference in its entirety for allpurposes. A system for incorporating transcoders is described incommonly assigned and co-pending U.S. patent application Ser. No.10/099,901, filed on Mar. 12, 2002, which is incorporated by referencein its entirety for all purposes. The introduction of additionaltranscoders allows for the decoupled advertising and negotiation of allcodecs that are fully supported in the mesh of transcoders supported inthe gateway. As terminal capabilities and codec capabilities increasehowever, the burden on the gateway system increases with each new codecadded as shown in Table 1. TABLE 1 Examples of transcoders utilized foradvertised capabilities A terminal B terminal Gateway support H.263H.263 H.263 to H.263 H.263 MP4-Visual H.263 to MP4-Visual MP4-Visual toH.263 H.263 H.263 H.263 to H.263 MP4-Visual H.263 to MP4-VisualMP4-Visual to H.263 H.263 H.263 H.263 to H.263 H.264 MP4-Visual H.263 toH.264 H.263 to MP4-Visual H.264 to H.263 H.264 to MP4-Visual MP4-Visualto H.263 MP4-Visual to H.264 H.263 H.263 H.263 to H.263 H.264 H.264H.263 to H.264 MP4-Visual MP4-Visual H.263 to MP4-Visual H.264 to H.263H.264 to H.264 H.264 to MP4-Visual MP4-Visual to H.263 MP4-Visual toH.264 MP4-Visual to MP4-Visual H.261 H.261 25 video transcoders H.263H.263 H.264 H.264 H.265 H.265 MP4-Visual MP4-Visual

Decoupled negotiation generally also requires special procedures for themedia to ensure the quality of the media is maintained, especially fortemporally coded media such as video with its intra coded frames. Ifmedia is allowed to flow on one side of the gateway before the otherside is ready to receive it, then at the time the terminal becomes readyto receive media, the gateway will be mid-stream between two temporaldecoder refresh points. The gateway could simply begin passing mediathrough to the other side, but this will very likely result in corruptedmedia being displayed on the decoding terminal, which may proveunacceptable to users of a service employing such a technique.

Some alternatives exist for this problem the first of which uses a “waitfor feature then let through” approach. Here, a minimal decoder, orsimple bitstream recognizer, inspects the media and determines if adecoder refresh point is available. For some codecs, this might be bysearching for picture start code and finding a picture coding type. Thiscan be done directly on the bitstream, or even on the adapted ormultiplexed media stream to reduce the need for as many resources in thesystem. Also, other packaging features such as RTP headers may be usedto identify the start of a refresh frame. After the refresh point isdetermined, the refresh point and all following media can simply bepassed through the other side, or can be transcoded for the other side.This feature may be located in a transcoder, or a full decoder.

The approach described above may suffer from a lengthy, possiblyindefinite, delay as the feature is waited upon in the media stream. Toavoid this delay, it is possible for the gateway to force the generationof the feature at the terminal by transmitting a picture video fastupdate request, such as an H.245 VideoFastUpdate-like message, thenfollowing the wait method.

The approach described above may still suffer from a substantial delay(around a round trip even when successful), and if a terminal isincapable of transmitting a refresh feature, if for example it isdelivering pre-encoded media, then a VideoFastUpdate-like (VFU) requestwill not generally be effective in expediting the feature delivery.

A feature to create local dynamic generation of decoder refresh pointsin a transcoder is described more fully in commonly assigned andco-pending U.S. patent application Ser. No. 10/762,829, filed on Jan.21, 2004, which is incorporated by reference in its entirety for allpurposes. The application discusses a case of handling video errors inan active media stream. Here this feature is extended to a gatewaysituation with quality of the initial media transmitted to a participantand the decoder refresh point feature is used to allow media to flowfrom one side to the gateway before the other side is capable ofreceiving it. When the other side notifies the gateway it is capable ofreceiving media, the feature is generated. The media may be deliveredalong with other necessary details to start a media session, such asdecoder configuration information (DCI) or parameter sets. In the caseof a decoupled call setup, as soon as media arrives, and regardless ofif the other side is ready to receive it, the media is being decoded, orbuffered back to a last known good decode point such as the last decoderrefresh point, and as soon as the receiving side becomes ready, adecoder refresh point can be immediately transmitted to the receivingterminal. This provides an extremely fast set up for overall media. Thisis shown for the media flowing from H.323 to H.324 in FIG. 2.

Once the gateway receives media from H.323, the media is buffered ordecoded or transcoded. When the H.324 device is ready (OLC Ackreceived), then an I-frame is generated at the decoupled gateway and themedia including the I-frame is transmitted from the gateway to theH.324. A benefit of methods as described herein is that rather thanpropagating a message to the H.323 device (e.g., an OLC Ack) beforemedia is transmitted from the gateway, the media is transmitted from thegateway to the H.324 device upon receipt of the OLCs Ack from the H.324device. Thus, there is no media delay as would be incurred iftransmission of media was delayed until after the OLCs Ack wastransmitted from the gateway to the H.323 device.

FIG. 3 is a simplified diagram illustrating a call setup procedurebetween an H.324-like device and an H.323-like device using a capabilitycoupled gateway according to an embodiment of the present invention. Inthe embodiment illustrated in FIG. 3, the capabilities in the TCS areselectively restricted by the gateway to provide a reduced set ofcapabilities for the two terminals. One such reduction would be toreduce the set offered by the gateway to a single capability of audioand single capability of video. A benefit provided by the selectiverestriction of the number of capabilities is that subsequent steps inthe setup process may be performed more rapidly. As the mediacapabilities offered can be pared back to only those codecs supported inthe gateway, the remainder of the negotiation can occur in a decoupledfashion at the faster rate supported by the protocol and the terminals.

In the embodiments illustrated in FIG. 3, the number of capabilities inthe TCS transmitted from the gateway after receiving both thecapabilities from both terminals are selectively restricted to just oneaudio capability and one video capability, as well as a single optionfor adaptation layer for each of the media types. Other embodimentsselectively reduce the number of TCS capabilities to greater numbers ofcapabilities less than the total number of possible capabilities. Aswill be evident to one of skill in the art, the reduction in the numberof capabilities and the requirements on the gateway are related, withfewer capabilities resulting in fewer transcoders being required. One ofordinary skill in the art would recognize many variations,modifications, and alternatives.

The TCS is reduced to provide a selected capability for the session. Thesession is established in a decoupled fashion, but the capabilities areselected to provide a compatible service. The gateway is capable ofreceiving and transmitting media in conformance with the selectedcapabilities.

If the gateway reduces the selection of capabilities so that only asingle media mode is capable of eventuating from the negotiation, then agateway may take advantage of being able to pre-allocate its resourcesat capability reception point.

The embodiment illustrated in FIG. 3 does not provide features to avoidmedia corruption as described in relation to FIG. 2. As a result, amedia synchronization point is provided at the gateway, incurring adelay in the general case. The media synchronization point at thegateway uses a notification from a terminal that it is capable ofreceiving media before a gateway will signify that it is ready to alsoreceive media by sending a message to the transmitting terminal that itis ready to receive. In this way, media freely flows from end to end,with a possible conversion/transcoding at the gateway, but without aconcern of clipping the media being transmitted at the gateway. In thefigure, this media synchronization point is shown in both directions.For the gateway to know that the H.324-like terminal is ready to decodethe media transmitted, the OLC Ack (with an MTE Ack for the multiplexingof the media) is sent from H.324-like terminal to the gateway. Thegateway can now safely indicate to the H.323 terminal that it is OK totransmit media, and it does this through its OLC Ack on the H.323 side.Media then is transmitted from the H.323 side and can be forwarded,possibly with transcoding or other processing, to the H.324 side. Thereverse direction media synchronization for media transmitted from H.324to H.323 is conducted in the same fashion with the two terminals' rolesreversed.

According to an embodiment of the present invention, a method ofestablishing a reduced setup time session through a gateway is provided.The session is conducted between a first terminal operating under afirst protocol and a second terminal operating under a second protocol.As an example, the first protocol and the second protocol may be a sameprotocol or a different protocol. Merely by way of example, the firstprotocol is an H.324-like protocol in one embodiment, such as H.324 or3G-324M. The second protocol may be a SIP-like protocol, an RTSP-likeprotocol, an H.323-like protocol, or an HTTP-like protocol.

The method includes receiving a first capability message transmittedfrom the first terminal to the gateway and receiving a second capabilitymessage transmitted from the second terminal to the gateway. The firstcapability message may be a terminal capability set message and thesecond capability message may be a terminal capability set message. Inan embodiment, the first capability message may be media, a fast connectmessage, or be contained in a call signaling message. Alternatively, thesecond capability message may be an SDP-like message or a DESCRIBEmessage depending on the application.

The method also includes processing the first capability message and thesecond capability message to form a third capability message associatedwith the first capability message and a fourth capability messageassociated with the second capability message.

The method further includes transmitting a third capability message fromthe gateway to the first terminal and transmitting a fourth capabilitymessage from the gateway to the second terminal. Embodiments of thepresent invention provide for paring back of capabilities. For example,the number of video capabilities in the third capability message may beless than the number of video capabilities in the first capabilitymessage, for example, a single video capability. Additionally, thenumber of audio capabilities in the third capability message may be lessthan the number of audio capabilities in the first capability message,for example, a single audio capability. Moreover, the number ofmultiplexer table entries in the third capability message may be lessthan the number of multiplexer table entries in the first capabilitymessage, for example a single multiplexer table entry. Additionally, theaudio, video, or other capabilities in the fourth capability message maybe pared back in a manner similar to that discussed above. One ofordinary skill in the art would recognize many variations,modifications, and alternatives.

Moreover, the method includes receiving a first request messagetransmitted from the second terminal to the gateway. The first requestmessage is related to a process for opening a second media channeladapted to support a transmission of a second media stream from thesecond terminal to the gateway. The first request message may beassociated with the second capability message and the fourth capabilitymessage. In an embodiment, the first request message is an open logicalchannel request.

The method also includes transmitting a second request message from thegateway to the first terminal. The second request message is related toa process for opening a first media channel adapted to support atransmission of a first media stream from the gateway to the firstterminal. The second request message may be associated with the firstcapability message and the third capability message. In an embodiment,the second request message is at least one of a multiplexer table entryrequest or an open logical channel request.

Transmitting the second request message is performed independent ofreceiving the first request message. For example, the second requestmessage may be transmitted from the gateway to the first terminal priorto receiving the first request message transmitted from the secondterminal to the gateway. In an embodiment, transmitting the secondrequest message from the gateway to the first terminal is performedindependent of the first request message being transmitted from thesecond terminal to the gateway. In another embodiment, transmitting thesecond request message from the gateway to the first terminal isperformed independent of the second terminal adopting a capabilityincluded in the fourth capability message.

Furthermore, the method includes receiving a first response messagetransmitted from the second terminal to the gateway. The first responsemessage is related to the process for opening the second media channel.In an embodiment, the first response message is an open logical channelacknowledgement. The method also includes transmitting a second responsemessage from the gateway to the first terminal. In an embodiment, thesecond response message is at least one of a multiplexer table entryacknowledgement or open logical channel acknowledgement. Transmittingthe second response message is performed in response to receiving thefirst response message.

In another embodiment, the method further includes transmitting a firstmedia stream between the first terminal and the gateway. The first mediastream is associated with the first media channel and is transmittedbetween the gateway and the second terminal. Additionally, the methodincludes transmitting a second media stream between the second terminaland the gateway. The second media stream is associated with the secondmedia channel and is transmitted between the gateway and the firstterminal.

It should be appreciated that the specific steps illustrated in FIG. 3provide a particular method of establishing a reduced setup time sessionthrough a gateway according to an embodiment of the present invention.Other sequences of steps may also be performed according to alternativeembodiments. For example, alternative embodiments of the presentinvention may perform the steps outlined above in a different order.Moreover, the individual steps illustrated in FIG. 3 may includemultiple sub-steps that may be performed in various sequences asappropriate to the individual step. Furthermore, additional steps may beadded or removed depending on the particular applications. One ofordinary skill in the art would recognize many variations,modifications, and alternatives.

FIG. 4 is a simplified diagram illustrating a call setup procedurebetween an H.324-like device and a SIP-like device using a capabilitycoupled gateway according to an embodiment of the present invention.Embodiments of the present invention provide the same two points in FIG.4 as described in relation to FIG. 3, especially in relation to theH.324 side. Here, the terminal capabilities expressed to the H.324 sidefrom the gateway, in the TCS(C) are coupled to the capabilityinformation and dependent on the capability information and gatewaydecisions related to the SIP terminal in its Session DescriptionProtocol (SDP), or a variation of SDP (SDP-like) information in theSDP(A) message.

The media synchronization point for media transmitted to the H.324 sideis shown where the gateway receives the OLC-Ack and propagates a SIP Ackfrom gateway to the SIP after the OLC Ack from the H.324-like terminalis received. At this point, you have the appropriate channelsestablished for the media and the media can be passed through thegateway.

In FIG. 4, the SIP terminal has pared the SDP transmitted from thegateway initially in SDP(A,B) back as illustrated in 2000K(SDP(A)). Thegateway initially transmitted an SDP message describing capabilitiesthat it would be able to support for a session established between thetwo ends. This does not mean it would need to support the full mesh aswould be required in the fully decoupled flow of FIG. 2, since, afterthe terminal has selected a mode on the SIP side, it uses thisinformation to determine the capabilities to transmit to the H.324 side.It is also possible that the information received from the SIP sidecould allow the gateway to transmit its TCS to the H.324 side withoutreceiving a TCS from the H.324 side. This may allow a slightly quickeroverall session setup if possible. For example, if the SIP determinationhas ended in a mode that the gateway can transcode to towards the H.324side. Or alternatively, if the SIP side selected a mandatory codec onthe other side, then the paring back could be performed and the messagetransmitted without concern for the incoming capabilities.

FIG. 5 is a simplified diagram illustrating an alternative call setupprocedure between an H.324-like device and a SIP-like device using acapability coupled gateway according to an embodiment of the presentinvention. This is similar to the flow shown in FIG. 4, but with a keydifference on how the gateway transmits its capabilities. Here, if aterminal supports the reception of an empty invite (an invite without anSDP-like content), which most terminals do (many early terminals wouldnot have accepted this empty invite and utilize the behavior associatedwith FIG. 4), the gateway holds back its capabilities, and insteadrequests that the SIP terminal describe its capabilities fully to thegateway before the gateway will answer with capabilities of its own. Themedia capabilities can then be synchronized as in FIG. 3 so that theTCS(C,D) from the H.324 side and the SDP(A,B) from the SIP side are bothreceived before the gateway describes its capabilities out to theterminals in the TCS(C) to the H.324 side and the Ack(A) to the SIPside. The media gateway could again pare back the capabilities to just asingle type and then pre-allocate some resources such as transcoders andallow the rest of the call setup to proceed in a decoupled fashion. Themedia synch point is the same in FIG. 5 as it was for FIG. 4.

In the situation in which a gateway receives an incoming INVITE with anSDP-like message from the SIP side, media negotiation would proceed viaan SDP-like protocol in the same way as this flow. If an incoming emptyINVITE was received at the gateway from the SIP-like side, then the flowwould be similar again to that shown in FIG. 4.

FIG. 6 is a simplified diagram illustrating a call setup procedurebetween an H.324-like device and an RTSP-like device using a capabilitycoupled gateway according to an embodiment of the present invention. Thesimilarities between the SIP and RTSP protocol are evident in thisfigure as the synchronization for media capability and mediasynchronization are very similar. Capability knowledge at the gatewayfrom the RTSP device is determined by an empty Ack equivalent, theDESCRIBE(URL), which will return the media description in the SDP(A,B).The H.324 side continues as described for FIG. 3. The mediasynchronization point is shown here by delaying the media transmissionat the RTSP server, allowed by a PLAY request, until an OLC Ack isreceived at the gateway.

Referring to the left-sides of FIGS. 3, 5, and 6, a method ofestablishing a reduced setup time session between an H.324-like terminaland a gateway is provided according to embodiments of the presentinvention The session operates under a predetermined protocol. Themethod includes receiving a second capability message transmitted from asecond terminal to the gateway and receiving a first capability messagetransmitted from the H.324-like terminal to the gateway. The method alsoincludes processing the first capability message to form a thirdcapability message associated with the first capability message. In anembodiment, the number of video capabilities in the second capabilitymessage is less than the number of video capabilities in the firstcapability message, for example, a single video capability. In anotherembodiment, the number of audio capabilities in the second capabilitymessage is less than the number of audio capabilities in the firstcapability message, for example, a single audio capability. In yetanother embodiment, the number of multiplexer table entries in thesecond capability message is less than the number of multiplexer tableentries in the first capability message, for example, a singlemultiplexer table entry.

The method further includes transmitting the third capability messagefrom the gateway to the H.324-like terminal after receiving the firstcapability message transmitted from the H.324-like terminal andreceiving the second capability message transmitted from the secondterminal to the gateway. Additionally, the method includes transmittinga request message from the gateway to the H.324-like terminal. Therequest message is related to a process for opening a media channelbetween the gateway and the H.324-like terminal and is transmittedindependent of the capability negotiation process between the gatewayand the second terminal. For example, the request message may include atleast one of a multiplexer table entry request or an open logicalchannel request.

Moreover, the method includes receiving a response message transmittedfrom the H.324-like terminal to the gateway. The response message isrelated to the process for opening the media channel and may include atleast one of a multiplexer table entry acknowledgement or open logicalchannel acknowledgement. The method also includes receiving a mediastream transmitted from the H.324-like terminal to the gateway using themedia channel and transmitting the media stream from the gateway to thesecond terminal. In an embodiment, the H.324-like terminal is a 3G-324Mhandset and the second terminal is either an H.323-like, an RTSP-like,or a SIP-like terminal.

Although the previous examples have been provided in the context of anH.324-like or an H.323-like terminal, utilizing appropriate protocols,this is not required by the present invention. In alternativeembodiments, other terminals, referred to as H.32X-like terminals areutilized. These H.32X-like terminals share common features, for example,the use of the H.245 control protocol. H.323-like and H.324-liketerminals are discussed herein as examples, but embodiments of thepresent invention provide method of utilizing other H.32X-like terminalsto reduce the setup times in sessions established through a gateway. Oneof ordinary skill in the art would recognize many variations,modifications, and alternatives.

FIG. 7 is a simplified diagram illustrating a call setup procedurebetween an H.324-like device and an H.323-like device using a capabilitycoupled gateway with a dynamic generation feature according to anembodiment of the present invention. As discussed in relation to FIG. 3,the capabilities from the H.324-like terminal and the H.323 terminal areused to determine the media capabilities that will be expressed by thegateway. TCS(C,D) and TCS(A,B) are both received before TCS(C) andTCS(A) are transmitted. However, the flow shown in FIG. 7 does notrequire a media synchronizations point, since the gateway contains thelocal generation of media decoder refresh points feature that wasdescribed with reference to FIG. 2. This allows the only coupling pointbetween the two sides to be the capability exchange and then allows therest of the negotiation to continue at maximum speed with no delaycaused by necessities at the gateway. The session establishment time formedia to be displayed is significantly better than the time shown wheretwo coupling points were used, as can be seen by comparing FIG. 7 toFIG. 3. The media local content feature may not necessarily be employedalways as the other side may indicate it is ready before the mediaarrives, but the ability to not impact the media with clipping andcorruption allows the session establishment to progress more quickly.

The media recovery options involving waiting for a feature are alsoapplicable to FIG. 7, but the session setup will be quickest if thelocal content generation feature is employed.

According to an embodiment of the present invention, a method ofestablishing a reduced setup time session through a gateway is provided.The session is conducted between a first terminal operating under afirst protocol and a second terminal operating under a second protocol.The method includes receiving a first capability message transmittedfrom the first terminal to the gateway and receiving a second capabilitymessage transmitted from the second terminal to the gateway.

The method also includes processing the first capability message and thesecond capability message to form a third capability message andprocessing the first capability message and the second capabilitymessage to form a fourth capability message.

The method further includes transmitting the third capability messagefrom the gateway to the first terminal and transmitting the fourthcapability message from the gateway to the second terminal.

Moreover, the method includes receiving a first request messagetransmitted from the second terminal to the gateway. The first requestmessage is related to a process for opening a second media channeladapted to support a transmission of a second media stream from thesecond terminal to the gateway. The method also includes transmitting asecond request message from the gateway to the first terminal. Thesecond request message is related to a process for opening a first mediachannel adapted to support a transmission of a first media stream fromthe gateway to the first terminal. Transmitting the second requestmessage is performed independent of receiving the first request message.

Furthermore, the method includes receiving a first response messagetransmitted from the second terminal to the gateway. The first responsemessage is related to the process for opening the second media channel.The method also includes transmitting a second response message from thegateway to the first terminal. Transmitting the second response messageis performed independent of receiving the first response message.

In an alternative embodiment, the method further includes performing atleast one of a buffering process to buffer the second media or adecoding process to decode the second media, receiving a third responsemessage transmitted from the first terminal to the gateway, andthereafter, transmitting the second media stream from the gateway to thefirst terminal. As an example, the second media stream may include anintra-code frame.

Utilizing embodiments of the present invention, the second media streamincludes a decoder refresh point, for example, an intra-coded frame. Insome embodiments, the second request message is transmitted from thegateway to the first terminal prior to receiving the first requestmessage transmitted from the second terminal to the gateway.

The various messages and processes performed in FIG. 7 may be or beperformed, in some embodiments, in a manner similar to that describedwith respect to FIG. 3. For example, the first request message mayinclude an open logical channel request and the first response messagemay include an open logical channel acknowledgement. The third responsemessage may include an OLC Ack. In a particular embodiment, the firstcapability message is a terminal capability set message and the secondcapability message is a terminal capability set message. Additionally,the second capability message may be an SDP-like message or a DESCRIBEmessage. The third capability message may be a terminal capability setmessage. Moreover, the first capability message is media, a fast connectmessage, or contained in a call signaling message in variousembodiments.

The first protocol and the second protocol may be the same protocol ordifferent protocols. Such protocols include an H.324-like protocol(e.g., H.324 or 3G-324M), an H.323-like protocol, a SIP-like protocol,an RTSP-like protocol, or an HTTP-like protocol. In some embodiments,capabilities are pared back so that the number of video capabilities inthe third capability message is less than the number of videocapabilities in the first capability message, for example, a singlevideo capability. The number of audio capabilities in the thirdcapability message may be less than the number of audio capabilities inthe first capability message, for example, a single audio capability.Additionally, the number of multiplexer table entries in the thirdcapability message may be less than the number of multiplexer tableentries in the first capability message, for example, a singlemultiplexer table entry. Moreover, the number of video capabilities inthe third capability message may be one, the number of audiocapabilities in the third capability message may be one, the number ofvideo capabilities in the fourth capability message may be one and thenumber of audio capabilities in the fourth capability message may beone.

It should be appreciated that the specific steps illustrated in FIG. 7provide a particular method of establishing a reduced setup time sessionthrough a gateway according to an embodiment of the present invention.Other sequences of steps may also be performed according to alternativeembodiments. For example, alternative embodiments of the presentinvention may perform the steps outlined above in a different order.Moreover, the individual steps illustrated in FIG. 7 may includemultiple sub-steps that may be performed in various sequences asappropriate to the individual step. Furthermore, additional steps may beadded or removed depending on the particular applications. One ofordinary skill in the art would recognize many variations,modifications, and alternatives.

Referring to the left side of FIG. 7, a method of establishing a reducedsetup time session between an H.324-like terminal and a gateway isprovided by an alternative embodiment of the present invention. Thesession operates under a predetermined protocol. The method includesreceiving a first capability message transmitted from the H.324-liketerminal to the gateway and receiving a second capability messagetransmitted from a second terminal to the gateway.

The method also includes processing the first capability message and thesecond capability message to form a third capability message andtransmitting the third capability message from the gateway to theH.324-like terminal. The method further includes transmitting the thirdcapability message from the gateway to the H.324-like terminal andtransmitting a first enablement message from the gateway to the secondterminal. The first enablement message is related to media transmissionenablement for a first media stream from the second terminal to thegateway and the first enablement message is transmitted prior toreceiving a second enablement message from the first terminal at thegateway. The second enablement message is related to media transmissionenablement for a second media stream from the gateway to the firstdevice.

The method also includes receiving a first media stream at the gateway,processing the first media stream at the gateway to provide a processedmedia stream, and transmitting the processed media stream as the secondmedia stream from the gateway. In a particular embodiment, the firstmedia stream is received prior to receiving the second enablementmessage. As an example, processing the media stream may includeidentifying a temporal feature in the media stream (e.g., an intra-codedframe) that enables a decoder to establish a decoder refresh point.Processing may also include generating an intra-coded frame at thegateway, for example, by converting an inter-coded frame into anintra-coded frame.

In another embodiment, processing the media steam further includesgenerating a VideoFastUpdate-like message and transmitting theVideoFastUpdate-like message from the gateway to the second terminal. Inyet another embodiment, processing the media stream includes generatingan intra-coded frame by converting an inter-coded frame into anintra-coded frame.

It should be appreciated that the specific steps illustrated in FIG. 7provide a particular method of establishing a reduced setup time sessionbetween an H.324-like terminal and a gateway according to an embodimentof the present invention. Other sequences of steps may also be performedaccording to alternative embodiments. For example, alternativeembodiments of the present invention may perform the steps outlinedabove in a different order. Moreover, the individual steps illustratedin FIG. 7 may include multiple sub-steps that may be performed invarious sequences as appropriate to the individual step. Furthermore,additional steps may be added or removed depending on the particularapplications. One of ordinary skill in the art would recognize manyvariations, modifications, and alternatives.

FIG. 8 is a simplified diagram illustrating a call setup procedurebetween an H.324-like device and an SIP-like device using a capabilitycoupled gateway with a dynamic generation feature according to anembodiment of the present invention. The session setup proceeds withcapability negotiation as discussed in relation to FIG. 4, then theaddition of the media recovery feature (likely the dynamic generationfeature for intra coded frames) at the gateway as described in relationto FIG. 7 allows for the removal of the media synchronization point(s)and a faster session setup with media recovery if any media arrivaltiming mismatches do occur. Again the decrease in setup time from FIG. 8to FIG. 4 is evident.

FIG. 20 is a simplified diagram illustrating a call setup procedurebetween an H.324-like device and a SIP-like device using a capabilitycoupled gateway with a dynamic generation feature according to anembodiment of the present invention. The session setup proceeds withcapability negotiation as discussed in relation to FIG. 5, then theaddition of the media recovery feature (likely the dynamic generationfeature for intra coded frames) at the gateway as described in relationto FIG. 7 allows for the removal of the media synchronization point(s)and a faster session setup with media recovery if any media arrivaltiming mismatches do occur. Again the decrease in setup time from FIG.20 to FIG. 5 is evident.

FIG. 9 is a simplified diagram illustrating a call setup procedurebetween an H.324-like device and an RTSP-like device using a capabilitycoupled gateway with a dynamic generation feature according to anembodiment of the present invention. Here, the RTSP device is acting asa media sink and is recording media from the H.324-like device. This maybe the case for a video weblog, or “blog,” or other upload service. Thesession setup is similar to that shown in relation to FIG. 6, but thereis also the addition of a local generation feature for media decoderrefresh points. Here, the session is established as quickly as possibleafter capabilities are coupled and decided at the gateway. Then, if theH.324-like device starts transmitting media before the RTSP device isready to record, a feature will be generated immediately upon sessionbeing ready to receive the media. This is particularly important featurefor the recording of video from a device as the intra coded frame needsto be present at the start of recorded media session for decent qualityin all the future playbacks.

This feature of local refresh point generation at the gateway canactually be employed at any time during a session when a recording isbeing made and this guarantees quality of the recorded media. It allowsfor better synchronization between the recorder and the terminal as thegateway has instantaneous response to the indication that an I-frameshould be sent based on service logic, and does not require a VFU toarrive at the handset. This should avoid clipping from the start of themedia due to delays.

FIG. 21 is a simplified diagram illustrating a call setup procedurebetween a first SIP-like device and a second SIP-like device using acapability coupled gateway according to an embodiment of the presentinvention. As discussed in relation to FIG. 5, the capabilities of bothSIP terminals are received at the gateway, in the form of an SDP(C,D)and SDP(A,B) before the gateway expresses its preferences via SDP(C) andAck(A). The gateway receives a full capability set from the terminal onthe right hand side due to its use of an empty INVITE. A mediasynchronization point exists and is dependent on the Ack from the lefthand side indicating that it is now capable of receiving media. This isthen propagated in the form of the Ack(A) to the right hand side, whichsends media, and the system operates without a concern of the mediabeing clipped.

FIG. 22 is a simplified diagram illustrating a call setup procedurebetween a first SIP-like device and a second SIP-like device using acapability coupled gateway with a dynamic generation feature accordingto an embodiment of the present invention. The flow is the same as withFIG. 21 initially but the media synchronization point is removed due tothe presence of the local feature generation ability. This relaxationallows for a much earlier transmission of the Ack(A). As can be seen incomparison to FIG. 21, the removal of the media synchronization pointallows for a fast session setup time end to end.

In an embodiment of the present invention, a method of establishing areduced setup time session between a first SIP-like terminal and asecond SIP-like terminal is provided. The session is conducted betweenthe first SIP-like terminal and the second SIP-like terminal through agateway. The method includes receiving a first call setup messagetransmitted from the first SIP-like terminal to the gateway. The firstcall setup message includes a first capability message. As an example,the first capability message may be an SDP-like message. The method alsoincludes transmitting a second call setup message from the gateway tothe second SIP-like terminal. For example, the second call setup messagemay include a second capability message, such as an empty INVITE.

The method further includes receiving a second capability messagetransmitted from the second SIP-like terminal to the gateway,transmitting a first capability response message from the gateway to thefirst SIP-like terminal, transmitting a second capability responsemessage from the gateway to the second SIP-like terminal, and receivinga media stream transmitted from the second SIP-like terminal to thegateway. As an example, transmitting the first capability responsemessage to the first SIP-like terminal may be performed after receivingthe second capability message transmitted from the second SIP-liketerminal to the gateway.

According to some embodiments, the capabilities are pared down in theresponse message. Thus, the number of video capabilities in the firstcapability response message may be less than a number of videocapabilities in the first capability message, for example, a singlevideo capability. Additionally, the number of audio capabilities in thefirst capability response message may be less than the number of audiocapabilities in the first capability message, for example a single audiocapability. Moreover, the number of multiplexer table entries in thefirst capability response message may be less than the number ofmultiplexer table entries in the first capability message, for example,a single multiplexer table entry.

Moreover, the method includes processing the media stream, receiving anacknowledgment message transmitted from the first SIP-like terminal tothe gateway, and thereafter, transmitting the processed media streamfrom the gateway to the first SIP-like terminal. The acknowledgementmessage is received at the gateway after transmitting the secondcapability response message. By way of example, receiving theacknowledgment message transmitted from the first SIP-like terminal tothe gateway may be performed independent of receiving the media streamtransmitted from the second SIP-like terminal to the gateway.

According to an embodiment, processing the media stream includesidentifying a temporal feature in the media stream that enables adecoder to establish a decoder refresh point. The feature may be anintra-coded frame. In another embodiment, processing the media steamfurther includes generating a VideoFastUpdate-like message andtransmitting the VideoFastUpdate-like message from the gateway to thesecond terminal. In yet another embodiment, processing the media streamincludes generating an intra-coded frame, for example, by converting aninter-coded frame into an intra-coded frame.

In an alternative embodiment, the method includes receiving a secondmedia stream transmitted from the first SIP-like terminal to the gatewayand transmitting the second media stream from the gateway to the secondSIP-like terminal.

It should be appreciated that the specific steps illustrated in FIG. 22provide a particular method of establishing a reduced setup time sessionbetween a first SIP-like terminal and a second SIP-like terminalaccording to an embodiment of the present invention. Other sequences ofsteps may also be performed according to alternative embodiments. Forexample, alternative embodiments of the present invention may performthe steps outlined above in a different order. Moreover, the individualsteps illustrated in FIG. 22 may include multiple sub-steps that may beperformed in various sequences as appropriate to the individual step.Furthermore, additional steps may be added or removed depending on theparticular applications. One of ordinary skill in the art wouldrecognize many variations, modifications, and alternatives.

In an alternative embodiment, a method of establishing a reduced setuptime session between a first SIP-like terminal and a second SIP-liketerminal is provided. The session is conducted through a gateway. Themethod includes performing a first session setup process between thefirst terminal and the gateway and performing a second session setupprocess between the second terminal and the gateway. The second sessionsetup process is performed independent of the first session setupprocess.

Performing the first session setup process may include receiving a firstINVITE message, which includes a first capabilities message, transmittedfrom the first SIP-like terminal to the gateway, processing the firstcapabilities message, transmitting a first capabilities response messagefrom the gateway to the first SIP-like terminal, and receiving anacknowledgment message transmitted from the first SIP-like terminal tothe gateway. Performing the second session setup process may includetransmitting a second INVITE message, which may be an empty INVITEmessage, from the gateway to the second SIP-like terminal, receiving asecond capabilities response message transmitted from the secondSIP-like terminal to the gateway, processing the second capabilitiesresponse message, and transmitting an acknowledgement message (e.g., anSDP-like message) from the gateway to the second SIP-like terminal.

The method also includes receiving a media stream transmitted from thesecond SIP-like terminal to the gateway, processing the first mediastream, providing an intra-coded frame, and thereafter, transmitting theintra-coded frame and the processed media stream from the gateway to thefirst SIP-like terminal. Processing the media stream may includeidentifying a temporal feature in the media stream that enables adecoder to establish a decoder refresh point. The temporal feature maybe an intra-coded frame, which may be generated by converting aninter-coded frame into an intra-coded frame. Additionally, the methodmay include generating a VideoFastUpdate or a VideoFastUpdate-likemessage and transmitting the VideoFastUpdate or VideoFastUpdate-likemessage from the gateway to the second terminal.

In a specific embodiment, the method additionally includes receiving asecond media stream transmitted from the first SIP-like terminal to thegateway and transmitting the second media stream from the gateway to thesecond SIP-like terminal. As discussed above, the number of videocapabilities, audio capabilities, and multiplexer table entries may bepared down by the gateway. In some embodiments, the number is pared downto a single capability or multiplexer table entry.

FIG. 10 is a simplified diagram illustrating a call setup procedurebetween a first device implementing an accelerated procedure and anH.324-like device implementing an accelerated procedure using a gatewayaccording to an embodiment of the present invention. After the gatewayreceives a fast setup capability from the first device, using any numberof session setup acceleration techniques, it begins to transmit itsH.324 related capabilities, based in part, upon the capabilitiesreceived from the left hand side. The most likely capabilitiesprocessing would be a reduction of known capabilities to produce a knownsession type in a similar way to shown in FIG. 4, where somecapabilities are likely needed to be expressed earlier than would bedesired for optimal capability negotiation. The behavior here could alsoproceed in a fully decoupled fashion as described in association withFIG. 2, taking advantage of the speed gain in the decoupledcapabilities, the removal of the need for a media synchronization point,and the speed associated with the pair of respective session setuptechniques.

FIG. 11 is a simplified call flow illustrating call establishment froman H.323 device implementing an accelerated procedure through a gatewayto an H.324-like device implementing an accelerated “fast setup”procedure according to an embodiment of the present invention.Embodiments of the present invention provide for decoupled operation inthe context of an H.323 fast connect+H.324 fast setup implementation. Asillustrated in FIG. 11, both the H.323 terminal and H.324-like terminalsupport “fast connect” and “fast setup” procedures, so the session maybe established in a smaller number of steps than conventional methodssince several procedures are aggregated into single messages on bothsides of the gateway. This is the method described in relation to FIG.10, but applied to the H.324 fast setup procedures described in U.S.Provisional Patent Application No. 60/433,252, filed on Dec. 12, 2002.

FIG. 12 is a simplified diagram illustrating a call setup procedurebetween an H.324-like device implementing an accelerated procedure and adevice implementing an accelerated procedure using a gateway accordingto an embodiment of the present invention. FIG. 12 is similar to FIG.10, but shows the session setup proceeding from a call originated fromthe H.324 side.

FIG. 13 is a simplified call flow illustrating call establishment froman H.324 device implementing an accelerated procedure through a gatewayto an H.323 device implementing an accelerated procedure according to anembodiment of the present invention. As illustrated in FIG. 13, someembodiments of the present invention support H.324 fast setup to H.323with fast connect. In these embodiments, the H.324 terminal support the“fast setup” extension and the call flow is illustrated in FIG. 13. Thisis the method described in relation to FIG. 12, but applied to the H.324fast setup procedures described in U.S. Provisional Patent ApplicationNo. 60/433,252, filed on Dec. 12, 2002.

Embodiments of the present invention provide a novel architecture forthe Decoupled Gateway Session Signaling (DGSS) function of a MultimediaGateway. The DGSS Architecture defines an Abstract Session Setup StateMachine. This abstract state machine applies to a variety of multimedianetworks and defines the session setup procedures in a general andwidely applicable way. The DGSS architecture also defines a functionaldecomposition of the Gateway Session Signaling (GSS) function thatincludes a Session Handler, which is an embodiment of the AbstractSession Setup State Machine, Protocol Wrappers, and concrete protocolimplementations. The interfaces between the Protocol Wrappers and theSession Handler are specified herein.

A characteristic of the Abstract Session State Machine is that itcontains only a few well-defined points where the two call halves mustbe synchronized. This allows much of the work involved in session setupto be done in parallel by the concrete protocols and their associatedProtocol Wrappers. The result is reduced coupling between call halvesand decreased session setup time compared to a Full Proxy GSSimplementation, described below.

Embodiments of the present invention described herein apply to H.324,H.324M, and 3G-324M and other systems that employ similar standards.Further, although some embodiments are described in the context ofconnecting such terminals to H.323, SIP, and RTSP terminals or services,the methods and systems can be applied to similar networks.

Due to the similarities that HTTP shares with RTSP (and SIP), sessionsetup would follow the same flow. However, the buffering of the fileretrieved from HTTP could additionally be performed at the gateway, orin a separate proxy or mediation entity. For depositing of HTTP files,the buffering and any additional processing, including transcoding andtransizing can be completed at the gateway or a proxy or mediationdevice before posting/putting the file on the HTTP server. Note thattranscoding, trans-sizing, trans-rating and other media adaptation canbe performed in the context of HTTP on the fly and in real time withouthaving to store the media in a temporary file.

The session handling method and apparatus described in this inventionachieves a fast session setup completion by allowing either side of thesession handler in a MMGW to proceed at its highest pace. Because amultimedia session involving terminating points using protocols such as3G-324M, SIP, H.323, RTSP, and the like require some form of capabilityand media mode exchange procedures, embodiments of the invention includesynchronization points that allow the session handler to synchronize thestate of each leg of the call (each terminating end to the MMGW). Thesynchronization permits connected terminals to achieve proper timing ofprotocol procedures and media exchange for channels carrying statefuldata (such as compressed video), so that a terminating end receivesmedia when it is ready and no initial media is lost, which may lead tosome unwanted artifacts common to video communication resulting fromlost of key frames.

The session handling method divides the session establishment into thefollowing phases separated by synchronization points:

-   -   Capability Exchange Phase;    -   Synchronization Point    -   Media Mode Selection    -   Synchronization Point    -   Media Exchange

The synchronization points are programming devices within the sessionhandler that allows it to wait until its procedures with each of theterminating endpoints to complete before the session handler proceeds tothe next phase.

When providing MMGW functionality, there are some important designgoals:

-   -   1. Call signaling and session signaling in the MMGW should occur        as quickly as possible. Delays on the order of a few hundred        milliseconds are generally tolerated by a human user, but setup        times of many seconds or longer result in poor user experience        and unnecessary waste of network resources.    -   2. The internal system architecture of the MMGW should be        flexible enough so that multiple and simultaneous network        interfaces can be supported.    -   3. The internal system architecture in the MMGW should be        flexible enough so that additional network capabilities can be        introduced over time as networks evolve or as new networks        appear. In practice, there is usually a layer of abstract        partitioning within the MMGW as well as well designed internal        interfaces between the partitioned components.    -   4. Some of the data carried over channels is inherently        ‘stateful’ and can result in poor performance or quality if the        data is transmitted by one party before it is ready to be        received by the other. In order to address this, the MMGW should        be able to either manage the synchronization of the channel        state between the two ends or manage the media itself so that        the state is preserved.

Capability Exchange Phase

During this phase each terminating endpoint transmits its capabilitiesusing its protocol procedures to the session handler. The capabilitiesmay include which media format it supports. For example for video, thecapabilities may include compression schemes, bit rates, frame rates,frame sizes. For audio, including voice, capabilities may includecompression scheme, bit rate, pre/post processing features, silencedetection, and the like. General data capabilities may also be included(e.g., fax, data sharing applications such as white-boarding). Thisphase may also include additional procedures that are needed by the nextphase (such as Master/Slave determination of the H.324 and H.323 systemprotocols, or multiplex capabilities of H.324).

The decoupling of the Capability Exchange allows each terminatingendpoint to complete its exchange procedures as fast it can with thesession handler. The capabilities transmitted by the session handler toeach of the terminating endpoints correspond to those it can handle oneach respective terminating end point. For example:

-   -   Mobile Terminal A supports H.263    -   Fixed Terminal/Server B supports MPEG4-video    -   The MMGW supports Mobile/H.263 to/from Fixed/MPEG4-video        transcoding    -   In this case the session handler transmits the (possibly pared        back) H.263 capabilities to Terminal A and MPEG4-video        capabilities to Terminal/Server B.

The Synchronization Point at the end of this procedure allows theCapabilities Exchange and other procedures to complete between eachterminating endpoint and the MMGW's session handler if needed and be ina position to proceed to the next phase.

Note that depending on the protocols used in either side of the MMGW,this synchronization point may or may not exist. That is, if a protocolon one side of the MMGW does not need to provide all the informationneeded to synchronize with the other side, then the MMGW may either holdthe synchronization until the information is available or supply defaultinformation or information provided by a network element (e.g. databaseof service) instead.

Media Mode Selection

During this phase each terminal, based on its capabilities and thatreceived from its peer (the MMGW's session handler), selects the mediamodes it intends to exchange and invokes the appropriate procedures toallow media exchange, including the opening of media channels and thedefinition of multiplex capabilities or the association of mediachannels with transport addresses and ports as required in the contextof a packet based system protocols such as H.323, SIP and RTSP.

The Synchronization Point at the end of this phase allows the sessionhandler and the terminating endpoints to complete their media modeselection and associated procedures as to be ready for media exchange.

Note that in the case of a content access services such as RTSP, thesession connectivity issues and the synchronization points would besimilar to SIP with the addition that in the context of RTSP, anexplicit command such as PLAY is used to explicitly instruct thestreaming server to start the media streaming.

Note that if the protocol or associated service (e.g. RTSP andstreaming) on one side of the MMGW does not provide specific informationfor the media selection, then the MMGW may provide default informationor supply information stored in a network element (e.g. database ofservice).

Media Exchange Phase

During this phase each terminal transmits its media to the MMGW whichtransforms it appropriately as to be conformant and understandable bythe other terminal.

It is not always required to delay the transmission of media from eitherendpoint to the gateway up until synchronization point, even forstateful media. The media gateway could in fact be receiving media fromone terminal prior to the determination that the other terminal iscapable of receiving the media. Typically, if the limit is notmaintained and media is simply passed through the media gateway prior tothe synchronization point, there is substantial degradation of themedia, as well as possible media synchronization/skew issues. However,if the gateway is capable of creating the stateful aspect of a mediastream dynamically (i.e., producing an output intra coded frame from aninter coded frame), then the synchronization point can cause thisfeature generation and then media transmission can continue. This allowsa faster setup time, as there is no need to wait for the furthersynchronization and media flow to propagate to the terminal and back.Instead, media is available immediately from the gateway which reducesoverall session setup time. Further discussion of the dynamic generationfeature is found in U.S. patent application Ser. No. 10/762,829, filedon Jan. 21, 2004, and entitled “Method And Apparatus for Handling VideoCommunications Errors,” the disclosure of which is incorporated hereinin its entirety for all purposes. Moreover, additional description ofthe dynamic generation feature is found in U.S. patent application Ser.No. 11/496,058, filed on Jul. 28, 2006, and entitled “Method andApparatus for Providing Interactive Media During Communication inChannel-Based Media Telecommunication Protocols,” the disclosure ofwhich is incorporated herein in its entirety for all purposes. Thisfeature is also useful for protocols that allow media transmissionbefore negotiation in an attempt to speed up session setup, such asH.320 or SIP early media or the media transmission features described inU.S. patent application Ser. No. 10/934,077, filed on Sep. 3, 2004, andentitled “Methods And System For Fast Session Establishment BetweenEquipment Using H.324 And Related Telecommunications Protocols” and U.S.patent application Ser. No. 11/303,858, filed on Dec. 15, 2005, andentitled “Fast Session Setup Extensions to H.324,” the disclosure ofwhich is incorporated herein in its entirety for all purposes. In thesecases, media cannot necessarily be delayed until it can be synchronizedend to end but the feature allows reception of the media and dynamicgeneration of the features when the far end point is capable ofreceiving them allowing the fastest possible setup time.

Note that the phases describe above can be repeated. For example if theterminals close their media channels, they can repeat the media modeselection phase to select different media configurations. When thephases are repeated, the session handler will use synchronization toensure proper readiness of terminals to be in the next phase (e.g. mediaexchange).

Embodiments of the present invention as described above and throughoutthe present specification are also applicable to other protocols thatcould be in use on either side of the gateway, regardless of whetherthey are circuit switched based or packet switched based. Embodimentsprovide principles to allow the session protocols on either side of thegateway to proceed as fast and as far as they can and to meet atsynchronization points where a protocol on one side of the gateway needsto ensure that the other protocol has completed the procedures neededbefore moving to the next phase of the session establishment. Henceembodiments of the invention are applicable to all protocols thatinvolve the establishment of a multimedia session that could involveexchange of video, audio, data, including messages such chat textmessages. One of ordinary skill in the art would recognize manyvariations, modifications, and alternatives.

An example embodiment of the invention is described below. Theembodiment architecture contains several discrete components:

-   -   1. The Session Handler, which implements the Abstract Session        State Machine and contains interfaces to the Call Signaling, the        Protocol Wrappers and the Media Gateway resources.    -   2. For each concrete protocol that is to be supported by the        MMGW (e.g., 3G-324M, but also including other protocols as        described above), a software implementation of that protocol is        required. A custom Protocol Wrapper is required for each        concrete protocol that mediates between the interfaces provided        by the concrete protocol and the Session Handler, according to        its specified interfaces.

Functional Decomposition of Decoupled Gateway Session Signaling

FIG. 15 illustrates components of a Decoupled Gateway Session SignalingArchitecture according to an embodiment of the present invention. Thesecomponents include a Session Handler, Protocol Wrappers, and Interfaces.Embodiments of the present invention are not limited to the componentsillustrated in FIG. 15, but may include additional or fewer componentsas appropriate to the particular application.

At the core of the Decoupled Session Gateway Signaling Architecture is aSession Handler. The Session Handler has interfaces to the CallSignaling, the Protocol Wrappers, and the media processing system, whichis typically called the Media Gateway. FIG. 15 depicts the relationshipof these entities when engaged in a single call from Network A toNetwork B. Note that both Network A and Network B may havenetwork-specific requirements and protocols for call signaling, sessionsignaling, and media transport and multiplexing.

The Protocol Wrappers convert protocol specific messages from the actualprotocol into protocol-independent messages relevant to the SessionSetup State Machine implemented by the Session Handler. The ProtocolWrappers provide a uniform and protocol-independent interface to each ofthe concrete protocol implementation supported by the MMGW. A specificProtocol Wrapper is required for each concrete protocol that needs to besupported. Variant Protocol Wrappers may also be used to accommodatedifferent actual protocol implementations or implementationenvironments. The protocol-independent representation is an internalrepresentation that is used to represent messages, states, andprocedures in a fashion independent of a specific standard protocol.

In the simplest case, the Call Signaling entity in the Media GatewayController does not concern itself with session signaling. All sessionsignaling is performed by the Session Handler. This is the normal(“normal start”) case. Some protocols, such as H.323 and H.324AnswerFast Type III terminals (AFIII), provide for mechanisms wheresession negotiation is either partly or completely completed as part ofCall Signaling. These are denoted are denoted here as “fast start” or“early capabilities” cases.

A further “fast start” mechanism supported by the present invention isthe AnswerFast Type IV preference messages transmitted immediately onbearer establishment. These can take the form of preferences,capabilities and even media.

Message Flows During Call Establishment

FIG. 16 illustrates message flows between various components of agateway during call establishment in some embodiments of the presentinvention.

When a new call arrives, the Call Signaling entity sends a message tothe Session Handler. The first message to the Session Handler (FIG.16/Reference Point 1) is a CreateCall_Req message.

The Session Handler initializes an internal state for this new call, andthen uses the incoming and outgoing call type to determine whichprotocols are to be used, and notifies the appropriate Protocol Wrappersto establish a new call.

Normal Start Call Signaling

The Session Handler then waits for the Protocol Wrappers to return theresult of their media option negotiation. It is the job of the ProtocolWrappers and Concrete Session Protocol implementations to negotiate anacceptable set of media options with their respective endpoints.Typically the Protocol Wrappers do not offer their media options, butinstead wait for the endpoints to offer their media options first. Thisnegotiation may involve many separate messages by the concreteprotocols, depending upon protocol. See FIG. 16/Reference Point 2 b.When this phase has been completed by a call leg, its Protocol Wrapperreports the results by a MediaOptions_Ind message (FIG. 16/ReferencePoint 3 b).

Fast Start and Early Capabilities

In some cases, it is possible to receive capabilities and sessionpreferences from the signaling layer. H.323 has FastConnect procedureswhich provide a way of tunneling an initial set of offered media optionsin the call signaling messages. Similarly, when using SIP, the mediacapabilities normally arrive in the form of a Session DescriptionProtocol (SDP), or a variation of SDP (SDP-like), message attachmentwith the initial INVITE message. In both cases, the offered mediaoptions are tunneled through the call signaling layer through theSession Handler.

Note that although the Session Handler does not normally offer upinitial media capabilities (and insists instead that the endpoints tooffer theirs first), there are a number of cases where this is notpractical. In Fast Start & Early Capabilities, it may be necessary insome cases to offer capabilities to the other endpoint as part of CallSignaling. An initial set of options may be determined in a wide varietyof ways, including provisioning a default set. Whether this happens, ornot, is immaterial, as long as the tunneled options are provided to theSession Handler at the CreateCall_Req message.

In all cases of Fast Start & Early Capabilities, the media options areessentially pre-negotiated, and are provided to the Session Handler inthe initial CreateCall_Req. The Session Handler, in turn, provides thisinformation to the Protocol Wrappers (FIG. 16/Reference Point 2 a).Because the information about offered media options has already beendetermined, the Protocol Wrappers are not required to perform anysession signaling. They simply parse the payload of these messages andimmediately reply to the Session Handler with the MediaOptions_Indmessage (FIG. 16/Reference Point 3 a).

Media Options Synchronization Point

Once the Session Handler has received the offered media capabilities, itdetermines an acceptable combination of options that can be provided bythe Media Gateway. For example, a mobile endpoint might offerMPEG4-video as its preferred video codec, and a packet client mightoffer H.263. The Media Gateway can only accept this call if it canperform MPEG4-video to/from H.263 transcoding. Of course, if anagreeable set of media options cannot be negotiated with eitherendpoint, the decision of how to proceed is context specific.

At this point, the Session Handler may need to reserve resources withinthe MMGW (and in particular, within the Media Gateway) to support thecall.

Following this stage a message is sent to each Protocol Wrapper (FIG.16/Reference Point 4) to specify which of the options are actuallychosen, and this notifies the Protocol Wrappers to continue with thecall and to allow the establishment of the media channels. The SessionHandler then enters the Session Ready state and logical channels may beopened.

The Protocol Wrappers then immediately attempt to open the logicalchannels associated with the call.

Opening Logical Channels

The Session Handler then instructs the Protocol Wrappers to open each ofthe negotiated logical channels. Logical channels are openedindependently, and fall into two main categories: those that requiresynchronization for proper operation and those that do not. When theProtocol Wrappers indicate to the Session Handler that the transmitterfor one logical channel is ready and the receiver for that logicalchannel is likewise ready, the Session Handler enables the Media Gatewayto start the flow of media for that channel.

Waiting for the transmitter and receiver for the logical channels toopen represents the second synchronization point for the call (moreprecisely, the second final set of ‘Media Channel Ready’ synchronizationpoints, as multiple unidirectional channels are typically opened). Inthe general case it is possible to handle channels that do not requiresynchronization without a new synchronization point between the protocolwrappers and simply synchronize the call on channels which do carry‘stateful’ data.

FIG. 17 is a simplified diagram of messaging flow between components ina gateway illustrating media activation in a media gateway according toan embodiment of the present invention. FIG. 17 illustrates a protocol“ladder diagram” between the Session Protocol Wrappers and the SessionHandler according to an embodiment of the present invention. FIG. 17illustrates both the “media options wait” synchronization point, and the“media channel ready” synchronization point for a single unidirectionallogical channel.

The flow shown in FIG. 17 can be mapped onto the external protocolbehavior of the gateway, and can be explained with reference to FIG. 3and FIG. 5. The media options are the internal gateway representation ofthe capability messages received at the gateway, in the form of TCS(C,D)or TCS(A,B)/SDP(A,B) in the referenced figures. These capabilitymessages are then processed, and possibly pared back to a selectedsubset. The selected media options are transmitted to protocol wrappersand eventually are transmitted to end devices in the TCS(C) andTCS(A)/SDP(A) capability messages.

The session handler receives an indication from the left hand protocolwrapper associated endpoint has changed state to be able to receivemedia. This could be, for example, in the form of an OLC (or an OLCAck). The session handler also receives an indication that the righthand terminal has changed state to be able to transmit. This could be inthe form, for example, of an OLC (or an OLC Ack). The session handlerthen recognizes that it can allow for the session media to be crosstransmitted and sends media activation events accordingly. This allowsthe transmitter to transmit the media and the gateway to copy through,or process the media and then transmit, with media synchronized and noconcern on corruption. Note that as shown in the figure, the sessionhandler operates from the gateway's perspective so the indication of anRx is the gateway's protocol handler indicating it may receive media.

FIG. 14 is a simplified messaging flow between components in a gatewayillustrating media activation in a media gateway supporting dynamicgeneration feature according to an embodiment of the present invention.As described with relation to FIG. 17, FIG. 14 relaxes the constraint onthe protocol wrappers in a way that corresponds with the change fromFIG. 3 to FIG. 7, with the introduction of the local generation feature.This may introduce a new message, or sub message, into the system thatallows for a transcoder to operate in a decode only fashion where themedia state is tracked and kept satisfactorily for a media refresh pointtransmission on demand, but no media is transmitted until an indicationis received that the receiving terminal is ready to receive media. Thiscorresponds to the “no output” and “start output” sub messages.

An indication is received at the session handler that the negotiationshave created a media channel that is capable of receiving media on atthe gateway. Instead of holding off the activation message, associatedmost likely with an OLC Ack or SIP Ack, the activation occurs and theassociated media path, probably a transcoder is put into a no outputstate. The state remains in the “no output” state, possibly receivingmedia and decoding or buffering or otherwise preparing for a mediarecovery action until a message comes in from a separate protocolwrapper that the remote device is now capable of receiving media. Thesession handler can then activate the protocol wrapper associated withthe receiving external terminal and allow for transmission to “startoutput” and achieve a faster call setup than possible with thesynchronization method described in relation to FIG. 17.

FIG. 18 illustrates how a state machine can control the establishment ofa session with synchronization points according to an embodiment of thepresent invention. The “media channel ready” synchronization point neednot be a limitation on the transmission of stateful media if a mediarecover mechanism and in particular if a dynamic generation feature ispresent at the gateway.

Messages

Table 2 shows example messages used by the session establishmenthandler, together with their description. TABLE 2 From Cell Agent toSession Handler CreateCall_Req Used to establish a new call. Thismessage can carry media and terminal capabilities. ModifyCall_Req Usedto modify the context of a call. Can carry media and terminalcapabilities, or out of band information (e.g., 323 UII messages or SIPINTO messages) DeletCall_Req Used to terminate a call. From SessionHandler to Call Agent CreateCall_Cfm Confirms a create request.ModifyCall_Cfm Confirms a modify request. ModifyCall_Ind Can be used tocarry out of band information (e.g., cause the Call Agent to forward a323 UII message, or to create a SIP INFO message). DeleteCall_CfmConfirms the termination of a call. From Stack to Protocol Wrapper:Protocol Specific Terminal_Capabilities_Inc Capabilities of remoteendpoint. Start_Media_Channel_Ind Media channel is established. Containsmedia type and direction: Rx, Tx or RxTx for bi-directional channels.Close_Logical channel_Ind Logical channel has closed.Video_Fast_Update_Ind Video fast update request received from endpoint.From Protocol Wrapper to Stack: Protocol SpecificTerminal_Capabilities_Req Capabilities of local stack to send to remoteOpen_Logical_Channel_Req Open logical channel Close_Logical_Channel_ReqClose logical channel Video_Fast_Update_Req Send out Video fast update(possibly not required) Protocol Wrapper to Session Handler: ProtocolIndependent MediaOptions_Ind Contains the codec options of theendpoints. This data structure will be the same generic representationas used by the stacks for media capabilities. This will require aconversion from SDP in the case of SIP. Media_Channel_Ready_IndIndicates that a media channel is ready. Contains: Media type (Audio,Video) and Direction: Rx, Tx, RxTx Session Handler to Protocol Wrapper:Protocol Independent Selected_Codecs_Req Selected Media Capabilities topass on to endpoint

Example Call Flow

FIG. 19 is a messaging flow between components in a gateway illustratingsession setup between an H.324-like terminal and a SIP-like terminal ina media gateway according to an embodiment of the present invention.FIG. 19 shows a call flow that includes the session signaling with thesynchronization points between a 3G-324M/H.324 terminal and a SIP UserAgent. Note a SIP User Agent can be the SIP protocol entity in aterminal or a server. This figure shows some of the pertinentinteractions between the components in a decoupled gateway and the SIPuser agent and the H.324 terminal.

While the present invention has been described with respect toparticular embodiments and specific examples thereof, it should beunderstood that other embodiments may fall within the spirit and scopeof the invention. The scope of the invention should, therefore, bedetermined with reference to the appended claims along with their fullscope of equivalents.

1. A method of establishing a reduced setup time session through agateway, the session being conducted between a first terminal operatingunder a first protocol and a second terminal operating under a secondprotocol, the method comprising: receiving a first capability messagetransmitted from the first terminal to the gateway; receiving a secondcapability message transmitted from the second terminal to the gateway;processing the first capability message and the second capabilitymessage to form a third capability message associated with the firstcapability message and a fourth capability message associated with thesecond capability message; transmitting a third capability message fromthe gateway to the first terminal; transmitting a fourth capabilitymessage from the gateway to the second terminal; receiving a firstrequest message transmitted from the second terminal to the gateway, thefirst request message being related to a process for opening a secondmedia channel adapted to support a transmission of a second media streamfrom the second terminal to the gateway; transmitting a second requestmessage from the gateway to the first terminal, the second requestmessage being related to a process for opening a first media channeladapted to support a transmission of a first media stream from thegateway to the first terminal, wherein transmitting the second requestmessage is performed independent of receiving the first request message;receiving a first response message transmitted from the second terminalto the gateway, the first response message being related to the processfor opening the second media channel; and transmitting a second responsemessage from the gateway to the first terminal, wherein transmitting thesecond response message is performed in response to receiving the firstresponse message.
 2. The method of claim 1 wherein transmitting thesecond request message from the gateway to the first terminal isperformed independent of the first request message being transmittedfrom the second terminal to the gateway.
 3. The method of claim 1wherein transmitting the second request message from the gateway to thefirst terminal is performed independent of the second terminal adoptinga capability included in the fourth capability message.
 4. The method ofclaim 1 wherein the second request message is associated with the firstcapability message and the third capability message.
 5. The method ofclaim 1 wherein the first request message is associated with the secondcapability message and the fourth capability message.
 6. The method ofclaim 1 wherein the second request message is transmitted from thegateway to the first terminal prior to receiving the first requestmessage transmitted from the second terminal to the gateway.
 7. Themethod of claim 1 wherein the second request message comprises at leastone of a multiplexer table entry request or an open logical channelrequest.
 8. The method of claim 1 wherein the first request messagecomprises an open logical channel request.
 9. The method of claim 1wherein the first response message comprises an open logical channelacknowledgement.
 10. The method of claim 1 wherein the second responsemessage comprises at least one of a multiplexer table entryacknowledgement or an open logical channel acknowledgement.
 11. Themethod of claim 1 further comprising: transmitting a first media streambetween the first terminal and the gateway, wherein the first mediastream is associated with the first media channel; and transmitting asecond media stream between the second terminal and the gateway, whereinthe second media stream is associated with the second media channel. 12.The method of claim 11 further comprising: transmitting the first mediastream between the gateway and the second terminal; and transmitting thesecond media stream between the gateway and the first terminal.
 13. Themethod of claim 11 further comprising establishing a mediasynchronization point after selecting the first media mode and selectingthe second media mode.
 14. The method of claim 13 wherein establishing amedia synchronization point comprises: receiving a first mediaenablement message from the second terminal, the media enablementmessage indicating that the second terminal is ready to receive media;and transmitting a second media enablement message from the gateway tothe first terminal, the media enablement message indicating that thegateway is ready to receive media.
 15. The method of claim 14 whereinthe first media enablement message comprises an open logical channelAck.
 16. The method of claim 15 wherein the second media enablementmessage comprise at least one of an open logical channel Ack, a SIP Ack,or an RTSP PLAY.
 17. The method of claim 1 wherein the first capabilitymessage comprises a terminal capability set message.
 18. The method ofclaim 17 wherein the second capability message comprises a terminalcapability set message.
 19. The method of claim 17 wherein the secondcapability message comprises an SDP-like message.
 20. The method ofclaim 17 wherein the second capability message comprises a DESCRIBEmessage.
 21. The method of claim 17 wherein the third capability messagecomprises a terminal capability set message.
 22. The method of claim 1wherein the first capability message comprises media.
 23. The method ofclaim 1 wherein the first capability message comprises a fast connectmessage.
 24. The method of claim 1 wherein the first capability messageis contained in a call signaling message.
 25. The method of claim 1wherein the first protocol and the second protocol are a same protocol.26. The method of claim 1 wherein the first protocol and the secondprotocol are a different protocol.
 27. The method of claim 1 wherein thefirst protocol comprises an H.324-like protocol.
 28. The method of claim27 wherein the H.324-like protocol comprises at least one of H.324 and3G-324M.
 29. The method of claim 1 wherein the first protocol comprisesan H.323-like protocol.
 30. The method of claim 1 wherein the secondprotocol is at least one of a SIP-like protocol, an RTSP-like protocol,an H.323-like protocol, or an HTTP-like protocol.
 31. The method ofclaim 1 wherein a number of video capabilities in the third capabilitymessage is less than a number of video capabilities in the firstcapability message.
 32. The method of claim 31 wherein the number ofvideo capabilities in the third capability message is one.
 33. Themethod of claim 31 wherein a number of audio capabilities in the thirdcapability message is less than a number of audio capabilities in thefirst capability message.
 34. The method of claim 33 wherein the numberof audio capabilities in the third capability message is one.
 35. Themethod of claim 34 wherein a number of multiplexer table entries in thethird capability message is less than a number of multiplexer tableentries in the first capability message, the number of multiplexer tableentries in the third capability message being equal to one.
 36. Themethod of claim 1 wherein a number of video capabilities in the thirdcapability message is one and a number of audio capabilities in thethird capability message is one.
 37. The method of claim 36 wherein anumber of video capabilities in the fourth capability message is one anda number of audio capabilities in the fourth capability message is one.38. A method of establishing a reduced setup time session through agateway, the session being conducted between a first terminal operatingunder a first protocol and a second terminal operating under a secondprotocol, the method comprising: receiving a first capability messagetransmitted from the first terminal to the gateway; receiving a secondcapability message transmitted from the second terminal to the gateway;processing the first capability message and the second capabilitymessage to form a third capability message; processing the firstcapability message and the second capability message to form a fourthcapability message; transmitting the third capability message from thegateway to the first terminal; transmitting the fourth capabilitymessage from the gateway to the second terminal; receiving a firstrequest message transmitted from the second terminal to the gateway, thefirst request message being related to a process for opening a secondmedia channel adapted to support a transmission of a second media streamfrom the second terminal to the gateway; transmitting a second requestmessage from the gateway to the first terminal, the second requestmessage being related to a process for opening a first media channeladapted to support a transmission of a first media stream from thegateway to the first terminal, wherein transmitting the second requestmessage is performed independent of receiving the first request message;receiving a first response message transmitted from the second terminalto the gateway, the first response message being related to the processfor opening the second media channel; and transmitting a second responsemessage from the gateway to the first terminal, wherein transmitting thesecond response message is performed independent of receiving the firstresponse message.
 39. The method of claim 38 further comprising:performing at least one of a buffering process to buffer the secondmedia or a decoding process to decode, in part, the second media;receiving a third response message transmitted from the first terminalto the gateway; and thereafter, transmitting the second media streamfrom the gateway to the first terminal.
 40. The method of claim 39wherein the second media stream comprises a decoder refresh point. 41.The method of claim 39 wherein the second media stream comprises anintra coded frame.
 42. The method of claim 38 wherein the second requestmessage is transmitted from the gateway to the first terminal prior toreceiving the first request message transmitted from the second terminalto the gateway.
 43. The method of claim 38 wherein the first requestmessage comprises an open logical channel request.
 44. The method ofclaim 43 wherein the first response message comprises an open logicalchannel acknowledgement.
 45. The method of claim 38 wherein the thirdresponse message comprises an open logical channel Ack.
 46. The methodof claim 38 wherein the first capability message comprises a terminalcapability set message.
 47. The method of claim 46 wherein the secondcapability message comprises a terminal capability set message.
 48. Themethod of claim 46 wherein the second capability message comprises anSDP-like message.
 49. The method of claim 46 wherein the secondcapability message comprises a DESCRIBE message.
 50. The method of claim46 wherein the third capability message comprises a terminal capabilityset message.
 51. The method of claim 38 wherein the first capabilitymessage comprises media.
 52. The method of claim 38 wherein the firstcapability message comprises a fast connect message.
 53. The method ofclaim 38 wherein the first capability message is contained in a callsignaling message.
 54. The method of claim 38 wherein the first protocoland the second protocol are a same protocol.
 55. The method of claim 38wherein the first protocol and the second protocol are a differentprotocol.
 56. The method of claim 38 wherein the first protocolcomprises an H.324-like protocol.
 57. The method of claim 56 wherein theH.324-like protocol comprises at least one of H.324 and 3G-324M.
 58. Themethod of claim 38 wherein the first protocol comprises an H.323-likeprotocol.
 59. The method of claim 38 wherein the second protocol is atleast one of a SIP-like protocol, an RTSP-like protocol, an H.323-likeprotocol, or an HTTP-like protocol.
 60. The method of claim 38 wherein anumber of video capabilities in the third capability message is lessthan a number of video capabilities in the first capability message. 61.The method of claim 60 wherein the number of video capabilities in thethird capability message is one.
 62. The method of claim 60 wherein anumber of audio capabilities in the third capability message is lessthan a number of audio capabilities in the first capability message. 63.The method of claim 62 wherein the number of audio capabilities in thethird capability message is one.
 64. The method of claim 63 wherein anumber of multiplexer table entries in the third capability message isless than a number of multiplexer table entries in the first capabilitymessage, the number of multiplexer table entries in the third capabilitymessage being equal to one.
 65. The method of claim 38 wherein a numberof video capabilities in the third capability message is one and anumber of audio capabilities in the third capability message is one. 66.The method of claim 38 wherein a number of video capabilities in thefourth capability message is one and a number of audio capabilities inthe fourth capability message is one.
 67. A method of establishing acommunication session through a gateway, the communication session beingconducted between a first terminal and a second terminal, the methodcomprising: performing a first capability negotiation process with thefirst terminal; performing a second capability negotiation process withthe second terminal, the second capability negotiation process beingperformed independent of the first capability negotiation process;receiving a media stream transmitted from the second terminal;processing the media stream; providing a first temporal feature thatenables a decoder to establish a decoder refresh point; and thereafter,transmitting the first temporal feature and the processed media streamto the first terminal.
 68. The method of claim 67 wherein processing themedia stream comprises identifying a second temporal feature in themedia stream that enables a decoder to establish a decoder refreshpoint.
 69. The method of claim 68 wherein the second temporal featurecomprises an intra-coded frame.
 70. The method of claim 68 furthercomprising generating a VideoFastUpdate-like message and transmittingthe VideoFastUpdate-like message from the gateway to the secondterminal.
 71. The method of claim 67 wherein providing a first temporalfeature comprises generating an intra-coded frame.
 72. The method ofclaim 71 wherein generating the intra-coded frame comprises convertingan inter-coded frame into an intra-coded frame.
 73. The method of claim67 wherein the first temporal feature is provided by the gateway. 74.The method of claim 73 wherein the first temporal feature comprises anintra-coded frame provided by a video transcoder.
 75. The method ofclaim 74 wherein the intra-coded frame provided by the video transcoderis created in response to a media enablement message transmitted fromthe first terminal to the gateway.
 76. The method of claim 75 whereinthe media enablement message is an open logical channel Ack.
 77. Themethod of claim 67 wherein: the first capability negotiation processcomprises the transmission of a first terminal capability set messagefrom the gateway to the first terminal; and the second capabilitynegotiation process comprises the transmission of a second terminalcapability set message from the gateway to the second terminal.
 78. Themethod of claim 67 wherein the first terminal comprises an H.324-liketerminal.
 79. The method of claim 78 wherein the H.324-like terminalcomprises a 3G-324M handset.
 80. A method of establishing a reducedsetup time session between an H.32X-like terminal and a gateway, thesession operating under a predetermined protocol, the method comprising:receiving a second capability message transmitted from a second terminalto the gateway; receiving a first capability message transmitted fromthe H.32X-like terminal to the gateway; processing the first capabilitymessage to form a third capability message associated with the firstcapability message; transmitting the third capability message from thegateway to the H.32X-like terminal after: receiving the first capabilitymessage transmitted from the H.32X-like terminal; and receiving thesecond capability message transmitted from the second terminal to thegateway; transmitting a request message from the gateway to theH.32X-like terminal, wherein: the request message is related to aprocess for opening a media channel between the gateway and theH.32X-like terminal; and transmitting the request message is performedindependent of the capability negotiation process between the gatewayand the second terminal; receiving a response message transmitted fromthe H.32X-like terminal to the gateway, the response message beingrelated to the process for opening the media channel; receiving a mediastream transmitted from the H.32X-like terminal to the gateway using themedia channel; and transmitting the media stream from the gateway to thesecond terminal.
 81. The method of claim 80 wherein the H.32X-liketerminal comprises at least one of an H.324-like or an H.323-liketerminal.
 82. The method of claim 80 wherein the second terminalcomprises at least one of an H.323-like terminal, an H.324-liketerminal,a SIP-like terminal, or an RTSP-like terminal.
 83. The method of claim80 wherein a number of video capabilities in the third capabilitymessage is less than a number of video capabilities in the firstcapability message.
 84. The method of claim 83 wherein the number ofvideo capabilities in the third capability message is one.
 85. Themethod of claim 80 wherein a number of audio capabilities in the thirdcapability message is less than a number of audio capabilities in thefirst capability message.
 86. The method of claim 85 wherein the numberof audio capabilities in the third capability message is one.
 87. Themethod of claim 86 wherein a number of multiplexer table entries in thethird capability message is less than a number of multiplexer tableentries in the first capability message, the number of multiplexer tableentries in the third capability message being equal to one.
 88. Themethod of claim 80 wherein a number of video capabilities in the thirdcapability message is one and a number of audio capabilities in thethird capability message is one.
 89. The method of claim 80 wherein therequest message comprises at least one of a multiplexer table entryrequest or an open logical channel request.
 90. The method of claim 80wherein the response message comprises at least one of a multiplexertable entry acknowledgement or open logical channel acknowledgement. 91.A method of establishing a reduced setup time session between anH.324-like terminal and a gateway, the session operating under apredetermined protocol, the method comprising: receiving a firstcapability message transmitted from the H.324-like terminal to thegateway; receiving a second capability message transmitted from a secondterminal to the gateway; processing the first capability message and thesecond capability message to form a third capability message;transmitting the third capability message from the gateway to theH.324-like terminal; transmitting a first enablement message from thegateway to the second terminal, the first enablement message beingrelated to media transmission enablement for a first media stream fromthe second terminal to the gateway, wherein the first enablement messageis transmitted prior to receiving a second enablement message from thefirst terminal at the gateway, the second enablement message beingrelated to media transmission enablement for a second media stream fromthe gateway to the first device; receiving the first media stream at thegateway; processing the first media stream at the gateway to provide aprocessed media stream; and transmitting the processed media stream asthe second media stream from the gateway.
 92. The method of claim 91further comprising receiving the first media stream prior to receivingthe second enablement message.
 93. The method of claim 91 whereinprocessing the media stream comprises identifying a temporal feature inthe media stream that enables a decoder to establish a decoder refreshpoint.
 94. The method of claim 93 wherein the temporal feature comprisesan intra-coded frame.
 95. The method of claim 93 further comprisinggenerating a VideoFastUpdate-like message and transmitting theVideoFastUpdate-like message from the gateway to the second terminal.96. The method of claim 91 wherein processing further comprisesgenerating an intra-coded frame.
 97. The method of claim 96 whereingenerating the intra-coded frame comprises converting an inter-codedframe into an intra-coded frame.
 98. A method of establishing a reducedsetup time session between a first SIP-like terminal and a secondSIP-like terminal, the session being conducted between the firstSIP-like terminal and the second SIP-like terminal through a gateway,the method comprising: receiving a first call setup message transmittedfrom the first SIP-like terminal to the gateway, wherein the first callsetup message includes a first capability message; transmitting a secondcall setup message from the gateway to the second SIP-like terminal;receiving a second capability message transmitted from the secondSIP-like terminal to the gateway; transmitting a first capabilityresponse message from the gateway to the first SIP-like terminal;transmitting a second capability response message from the gateway tothe second SIP-like terminal; receiving a media stream transmitted fromthe second SIP-like terminal to the gateway; processing the mediastream; receiving an acknowledgment message transmitted from the firstSIP-like terminal to the gateway, wherein the acknowledgement message isreceived at the gateway after transmitting the second capabilityresponse message; and thereafter, transmitting the processed mediastream from the gateway to the first SIP-like terminal.
 99. The methodof claim 98 wherein the first capability message comprises an SDP-likemessage.
 100. The method of claim 98 wherein the second call setupmessage includes a second capability message.
 101. The method of claim98 wherein the second call setup message comprises an empty INVITE. 102.The method of claim 98 further comprising: receiving a second mediastream transmitted from the first SIP-like terminal to the gateway; andtransmitting the second media stream from the gateway to the secondSIP-like terminal.
 103. The method of claim 98 wherein transmitting thefirst capability response message to the first SIP-like terminal isperformed after receiving the second capability message transmitted fromthe second SIP-like terminal to the gateway.
 104. The method of claim 98wherein a number of video capabilities in the first capability responsemessage is less than a number of video capabilities in the firstcapability message.
 105. The method of claim 104 wherein the number ofvideo capabilities in the first capability response message is one. 106.The method of claim 98 wherein a number of audio capabilities in thefirst capability response message is less than a number of audiocapabilities in the first capability message.
 107. The method of claim106 wherein the number of audio capabilities in the first capabilityresponse message is one.
 108. The method of claim 98 wherein processingthe media stream comprises identifying a temporal feature in the mediastream that enables a decoder to establish a decoder refresh point. 109.The method of claim 108 wherein the temporal feature comprises anintra-coded frame.
 110. The method of claim 108 further comprisinggenerating a VideoFastUpdate-like message and transmitting theVideoFastUpdate-like message from the gateway to the second terminal.111. The method of claim 98 wherein processing further comprisesgenerating an intra-coded frame.
 112. The method of claim 111 whereingenerating the intra-coded frame comprises converting an inter-codedframe into an intra-coded frame.
 113. The method of claim 98 whereinreceiving an acknowledgment message transmitted from the first SIP-liketerminal to the gateway is performed independent of receiving the mediastream transmitted from the second SIP-like terminal to the gateway.114. A method of establishing a reduced setup time session between afirst SIP-like terminal and a second SIP-like terminal, the sessionbeing conducted through a gateway, the method comprising: performing afirst session setup process between the first terminal and the gateway;performing a second session setup process between the second terminaland the gateway, the second session setup process being performedindependent of the first session setup process; receiving a media streamtransmitted from the second SIP-like terminal to the gateway; processingthe first media stream; providing an intra-coded frame; and thereafter,transmitting the intra-coded frame and the processed media stream fromthe gateway to the first SIP-like terminal.
 115. The method of claim 114further comprising: receiving a second media stream transmitted from thefirst SIP-like terminal to the gateway; and transmitting the secondmedia stream from the gateway to the second SIP-like terminal.
 116. Themethod of claim 114 wherein performing the first session setup processcomprises: receiving a first INVITE message transmitted from the firstSIP-like terminal to the gateway, wherein the first INVITE messageincludes a first capabilities message; processing the first capabilitiesmessage; transmitting a first capabilities response message from thegateway to the first SIP-like terminal; and receiving an acknowledgmentmessage transmitted from the first SIP-like terminal to the gateway.117. The method of claim 116 wherein a number of video capabilities inthe first capability response message is less than a number of videocapabilities in the first capability message.
 118. The method of claim117 wherein the number of video capabilities in the first capabilityresponse message is one.
 119. The method of claim 116 wherein a numberof audio capabilities in the first capability response message is lessthan a number of audio capabilities in the first capability message.120. The method of claim 119 wherein the number of audio capabilities inthe first capability response message is one.
 121. The method of claim114 wherein performing the second session setup process comprises:transmitting a second INVITE message from the gateway to the secondSIP-like terminal; receiving a second capabilities response messagetransmitted from the second SIP-like terminal to the gateway; processingthe second capabilities response message; and transmitting anacknowledgement message from the gateway to the second SIP-liketerminal.
 122. The method of claim 121 wherein the second INVITE messagecomprises an empty INVITE message.
 123. The method of claim 121 whereinthe acknowledgment message includes an SDP-like message.
 124. The methodof claim 123 wherein a number of video capabilities in the SDP-likemessage is less than a number of video capabilities in the secondcapability response message.
 125. The method of claim 124 wherein thenumber of video capabilities in the SDP-like message is one.
 126. Themethod of claim 123 wherein a number of audio capabilities in theSDP-like message is less than a number of audio capabilities in thesecond capability response message.
 127. The method of claim 126 whereinthe number of audio capabilities in the SDP-like message is one. 128.The method of claim 114 wherein processing the media stream comprisesidentifying a temporal feature in the media stream that enables adecoder to establish a decoder refresh point.
 129. The method of claim128 wherein the temporal feature comprises an intra-coded frame. 130.The method of claim 128 further comprising generating aVideoFastUpdate-like message and transmitting the VideoFastUpdate-likemessage from the gateway to the second terminal.
 131. The method ofclaim 114 wherein processing further comprises generating an intra-codedframe.
 132. The method of claim 131 wherein generating the intra-codedframe comprises converting an inter-coded frame into an intra-codedframe.